Variable transmittance optical devices

ABSTRACT

A self-powered variable transmittance optical device, such as a smart window or other device, and associated method are provided. The device comprises one or more transparent substrates, with a switching material disposed thereon or therebetween. The switching material may be a hybrid photochromic/electrochromic material capable of transitioning from a first transmittance state to a second transmittance state with application of electricity, and from second state to first state due to another stimulus, such as UV radiation. Electrodes are coupled to the switching material for applying electricity. An electrical system provides for controllable application of the electricity, and may store energy. Energy is provided by an energy-harvesting power source such as a solar cell or other photovoltaic source, or array thereof, or another device for harvesting vibrational or thermal energy. Energy harvesting, energy storage capacity and/or switching material may be configured to provide at least a predetermined level of device operability.

RELATED CASES

This application is a National Stage Application of PCT/CA2011/001377,filed Dec. 15, 2011, which claims benefit of U.S. ProvisionalApplication No. 61/423,524 filed Dec. 15, 2010, and which applicationsare incorporated herein by reference. To the extent appropriate, a claimof priority is made to each of the above disclosed applications.

FIELD OF THE INVENTION

The present invention relates generally to variable transmittanceoptical filters and devices comprising such filters. The devices mayfurther comprise a power source.

BACKGROUND OF THE INVENTION

Optical filters have been used in glazings in window technology tocontrol the flow of light and heat through the glazing. Such filters maybe used on any sort of window, including those in buildings, vehicles,aircraft, spacecraft, ships or the like. Optical filters have also beenused to regulate lighting and heating levels, for glare reduction, andenergy load management. As an example, buildings consume over one thirdof all energy and over two-thirds of the electricity used in the UnitedStates, and are responsible for about one third of all greenhouse gas(GHG) emissions, as well as about 30% of a building's energy loss. Assuch, windows with improved technology for reducing heat loss and solarheat gain can offer significant benefits and cost savings.

Optical filters have also found application in ophthalmic devices tocontrol the light impacting the eye. Opthalmic applications include, forexample, prescription and non-prescription glasses, goggles, sunglasses,visors, and safety eyewear.

There are a number of technologies that have been used in opticalfilters and related devices and applications for dynamically varying thedegree of visible light transmittance, including photochromics,electrochromics, liquid crystals, thermochromics, and suspended particledisplays.

Electrochromic, liquid crystal, and suspended particle displays ordevices may be switched between states of high light transmissibility toone of a lower light transmissibility (or opacity/increased lightscattering for some devices) by application of electricity. Suchexisting power source and wiring may be used in this manner, and may notbe inconvenient when a building is designed to accommodate windows orscreens comprising such devices, it may necessitate an undesired amountof routing of electrical cables to the device, or cumbersomeretrofitting of wiring to accommodate optical filters put in place aftera building is constructed. Where the optical filter is used in awearable device (e.g. opthalmic devices) portability of the power sourceis an important factor. Thus, devices with a need for high voltage or abulky power source may not be suitable.

Several concepts for solar-powered windows have been described. Forexample, U.S. Pat. No. 4,475,031 discloses a sun-sensitive windowcomprising liquid nematic crystals powered directly by a solar cell.U.S. Pat. No. 5,384,653 discloses an electrochromic window powered by anarray of photovoltaic cells deposited along an edge of the window pane.U.S. Pat. No. 5,805,330 discloses an electro-optic window powered solelyby photovoltaic cells placed within the window area. U.S. Pat. No.6,055,089 discloses an electrochromic window powered by photovoltaiccells positioned so that at least part of the incident light on thecells passes through the electrochromic device, providing a form offeedback control. U.S. Pat. No. 6,297,900 discloses a smart windowcomprising a regenerative photoelectrochromic photovoltaic power sourceelement covering the window area co-extensively with an electrochromicwindow element.

Some electrochromic devices require continuous power to maintain thedark or faded state, and the power demand may increase with increasingsize of the device, particularly windows. For a solar-powered window, aphotovoltaic power source with a surface area of sufficient size to meetthe device's power requirement may be of an impractical size, and/orprohibitively expensive. If the photovoltaic power source is on a frameor pane of a window or lens, it may interfere with aspects such aswindow viewability. As photovoltaic power sources are dependent on theavailable amount of incident light, some lighting conditions may notconsistently provide sufficient incident light to generate sufficientpower for operation. Finally, even with self-contained photovoltaicpower sources, the solutions identified in the past may not provide anadequate means for retrofitting existing buildings with smart windowtechnology.

Therefore there is a need for a solution that overcomes at least one ofthe deficiencies in the art.

SUMMARY OF THE INVENTION

The present invention relates generally to variable transmittanceoptical filters and devices comprising such filters. The devices mayfurther comprise a power source.

In accordance with one aspect of the invention, there is provided adevice comprising: a variable transmittance optical filter, a powersource; and an electrical system configured to receive power from thepower source and to provide a voltage to a first electrode and a secondelectrode of the variable transmittance optical filter.

In accordance with another aspect of the invention, there is provided aninsert window comprising a frame defining an insert window area, avariable transmittance optical filter suspended within the frame, oversubstantially all the insert window area; and an electrical systemconfigured to receive power from a power source and to provide a voltageto a first and a second electrode of the variable transmittance opticalfilter.

In accordance with another aspect of the invention, there is provided aninsert window comprising: a variable transmittance optical filter, apane having the variable transmittance optical filter disposed on afirst side; and an electrical system configured to receive power from apower source and to provide a voltage to a first and a second electrode.

In accordance with another aspect of the invention there is provided aninsert window comprising: a variable transmittance optical filterdisposed on a first pane; a first frame holding the first pane andconfigured for slidably mounting in a second frame, the second frameconfigured for mounting adjacent to an existing window of a building;and a fastening system for mounting the second frame adjacent to theexisting window.

In accordance with another aspect of the invention, there is provided amethod of transitioning the device or the insert window from a darkstate to a light state comprising the steps of: providing an input fortransitioning the device to the control system, the input activating aswitch of the control system; and applying power from the power sourceto the electrodes of the device via the electrical system, the powersufficient to effect transition of the switching material from the darkstate to a light state.

In accordance with another aspect of the invention, there is provided amethod of operating a smart window comprising the steps of: providing avariable transmittance optical filter; providing a power source and anelectrical system configured to receive power from the power source andto provide a voltage to a first electrode and a second electrode of thevariable transmittance optical filter; and providing an input to operatea switch, the switch electrically connecting and applying a voltage fromthe power source to the first and second electrodes of the variabletransmittance optical filter; and activating the switch.

The variable transmittance optical filter may comprise a firstsubstantially transparent substrate comprising a first electrode, asecond substantially transparent substrate comprising a secondelectrode; a switching material disposed between, and operativelycoupled to, the first and second electrodes, the switching materialtransitionable from a first light transmittance state to a second lighttransmittance state with application of voltage to the switchingmaterial, and transitionable from the second light transmittance stateto the first light transmittance state with application of a secondnon-electrical stimulus.

In accordance with an aspect of the present invention, there is provideda self-powered variable transmittance optical device comprising: asubstantially transparent substrate; a switching material disposed onthe substrate, the switching material configured to transition from afirst transmittance state to a second transmittance state due at leastin part to application of an electric voltage, the switching materialconfigured to transition from the second transmittance state to thefirst transmittance state due at least in part to a stimulus other thanthe electric voltage; a first and second electrode operatively coupledto the switching material; an energy-harvesting power source; and anelectrical system configured to receive power from the energy-harvestingpower source and to provide power to the first electrode and the secondelectrode for application of the electric voltage.

In accordance with another aspect of the present invention, there isprovided a self-powered variable transmittance optical devicecomprising: a substantially transparent substrate; a switching materialdisposed on the substrate, the switching material capable oftransitioning between a light state and a dark state based at least inpart on application of an electric voltage; a first and second electrodeoperatively coupled to the switching material; an energy-harvestingpower source; and an electrical system configured to receive power fromthe energy-harvesting power source and to provide power to the firstelectrode and the second electrode for application of the electricvoltage.

In accordance with another aspect of the present invention, there isprovided a self-powered variable transmittance optical device filmcomprising: a substantially transparent and flexible substrate; aswitching material flexibly disposed on the substrate, the switchingmaterial capable of transitioning between a light state and a dark statebased at least in part on application of an electric voltage; a firstand second electrode operatively coupled to the switching material; anenergy-harvesting power source flexibly disposed on the device film; andan electrical system configured to receive power from theenergy-harvesting power source and to provide power to the firstelectrode and the second electrode for application of the electricvoltage, the electrical system flexibly disposed on the device film.

In accordance with another aspect of the present invention, there isprovided a method for preparing a self-powered variable transmittanceoptical device, the method comprising: disposing a layer of switchingmaterial on a substantially transparent substrate, the switchingmaterial capable of transitioning from a light state to a dark state onexposure to UV radiation and from a dark state to a light state withapplication of an electric voltage, wherein a first and second electrodeare disposed such that the switching material is proximate with thefirst and second electrodes; providing an energy-harvesting powersource; and providing an electrical system configured to receive powerfrom the energy-harvesting power source and to provide power to thefirst electrode and the second electrode for application of the electricvoltage through the first and second electrodes.

In accordance with another aspect of the present invention, there isprovided a method for preparing a self-powered variable transmittanceoptical device, the method comprising: disposing a layer of switchingmaterial on a substantially transparent substrate, the switchingmaterial capable of transitioning between a light state and a dark statebased at least in part on application of an electric voltage, wherein afirst electrode and a second electrode are disposed such that theswitching material is proximate with the first and second electrodes;providing an energy-harvesting power source; and providing an electricalsystem configured to receive power from the energy-harvesting powersource and to provide power to the first electrode and the secondelectrode for application of the electric voltage through the first andsecond electrodes.

In accordance with another aspect of the present invention, there isprovided a method for preparing a self-powered variable transmittanceoptical device film, the method comprising: disposing a layer ofswitching material on a substantially transparent and flexiblesubstrate, the switching material capable of transitioning between alight state and a dark state based at least in part on application of anelectric voltage, wherein a first electrode and a second electrode areflexibly disposed such that the switching material is proximate with thefirst and second electrodes; disposing a flexible energy-harvestingpower source on the device film; and disposing a flexible electricalsystem on the device film, the electrical system configured to receivepower from the energy-harvesting power source and to provide power tothe first electrode and the second electrode for application of theelectric voltage.

Aspects of the invention may be advantageous in reducing solar heat gainand/or reducing cooling loads in buildings, vehicles and transitsystems. Aspect of the invention may be useful as variable glare- orlight-reducing lenses or visors of opthalmic devices. The darkeningresponse to UV light does not require power input, and theelectrochromic fading is effected with very low power demands that maybe met by small, portable or wearable, energy harvesting power sources.

This summary of the invention does not necessarily describe all featuresof the invention. Other aspects, features and advantages of the presentinvention will become apparent to those of ordinary skill in the artupon review of the following description of specific embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent fromthe following description in which reference is made to the appendeddrawings wherein:

FIG. 1 is a cross-sectional schematic view of an optical filter portionof an optical device according to an embodiment of the presentinvention;

FIG. 2 is a schematic view of a curved variable transmittance opticalfilter according to an embodiment of the present invention;

FIG. 3A, 3B illustrate a self-powered variable transmittance opticaldevice film, in accordance with an embodiment of the present invention;

FIG. 4A, B schematically illustrates embodiments of an electrical systemof a self-powered variable transmittance optical device, in accordancewith an embodiment of the present invention;

FIG. 5 provides a diagrammatic view showing the transmission of lightthrough a variable tint window in A) a dark state, and B) a light state,according to an embodiment of the present invention;

FIG. 6 is a cross-sectional schematic view of a variable transmittancewindow according to an embodiment of the present invention;

FIG. 7 is a cross-sectional schematic view of a variable transmittancewindow according to another embodiment of the present invention;

FIG. 8 illustrates a partial cross-section of a self-powered window, inaccordance with an embodiment of the present invention;

FIG. 9 illustrates a partial cross-section of a self-powered window, inaccordance with another embodiment of the present invention;

FIG. 10 illustrates a portion of a self-powered window, in accordancewith another embodiment of the present invention;

FIG. 11 is a general view of an ophthalmic device according to anembodiment of the present invention;

FIG. 12 illustrates the response of a hybrid photochromic/electrochromicoptical filter to application of voltage, in accordance with embodimentsof the present invention;

FIG. 13 shows an exemplary plot of the absorbance spectra of a hybridphotochromic/electrochromic switching material according to Formulation#2, comprising compound S054. Faded state (solid line); darkened using a365 nm light source without (open circle) or with (open square)EnergyFilm™; and darkened using a solar simulator without (solid circle)or with (solid square) EnergyFilm™;

FIG. 14A shows a plot of power requirements for devices of a range ofsizes (m²), according to various embodiments of the invention. FIG. 14Bshows a plot of the power requirement per unit area (W/m²) relative todevice size (m²), for devices according to various embodiments of theinvention;

FIG. 15 shows an insert window according to one embodiment of theinvention;

FIG. 16 shows an insert window according to another embodiment of theinvention;

FIG. 17 shows an insert window according to another embodiment of theinvention;

FIG. 18 shows an insert window according to another embodiment of theinvention;

FIG. 19 shows, for window configurations A-F, bar graphs of A) visiblelight transmittance (VLT) of the modeled windows—x axis indicates thewindow configuration modeled, y axis is the VLT (hatched bars—window indark state; solid bar—window in faded state); B) solar heat gaincoefficient (SHGC) of the modeled windows—x axis indicates the windowconfiguration modeled, y axis is the unitless SHGC values (hatchedbars—window in dark state; solid bar—window in faded state); C) U-value(W/m²-K) of the modeled window—x axis indicates the window configurationmodeled, y axis is the U-value; and

FIG. 20 shows a bar graph illustrating the energy used for an officebuilding modeled using the DoE EnergyPlus package in four cities, withfour window configurations. Y axis is Annual Energy use in kWh. Stripedbars—single pane window with no insert; solid bar; single pane windowwith single pane insert window comprising variable transmittance opticalfilter (equivalent to configuration B-2); checked bars—double pane IGUsmart insert window with variable transmittance optical filter(configuration E above; open bars—single pane clear insert window withfloat glass and low-E coatings or any variable transmittance.

DESCRIPTION OF THE INVENTION

The invention relates, in part, to a variable transmittance optical(VTO) filter (“optical filter”) and devices comprising such filters. TheVTO filter is electrically coupled to an electrical system, andoptionally to a power source. The invention also relates, in part, to adevice comprising a VTO filter, electrically coupled to an energyharvesting power source. The invention also relates to an insert windowcomprising a VTO filter electrically coupled to an electrical system,and optionally to a power source.

The invention provides, in part, a variable transmittance optical (VTO)device comprising an energy harvesting power source (a “self-powered”VTO device), the device capable of transitioning between a dark stateand a light state with application of a voltage to the device. In someembodiments, the device may transition from a light state to a darkstate with application of a voltage, or from a dark state to a lightstate with application of a voltage. In some embodiments, the device maytransition from a light state to a dark state on exposure to a lightsource and from a dark state to a light state with application of anelectric voltage. In some embodiments, the device may transition from alight state to a dark state on exposure to a light source, and from adark state to a light state with application of power (voltage) andexposure to a light source. The light source may provide UV light aloneor in combination with VIS and/or IR light.

The invention further provides, in part, a device comprising a VTOfilter, an energy harvesting power source and an electrical systemconfigured to receive power from the energy harvesting power source andto provide a voltage to first and second electrodes of the VTO filter,thereby transitioning the optical filter from a dark state to a lightstate.

In some embodiments, the device may be a window, an opthalmic device, anoptical filter, a display, signage or the like. The terms “smart window”and “variable transmittance window” may optionally be used to refer toan architectural, vehicle, or other window having a dynamic componentthat can darken and lighten according to a stimulus. Instead of beingfixed, the visible light transmittance of the window, or apportion ofthe window, may be variable. The window may be an insulated glazing unit(IGU) or an insert window.

Thus, the invention further provides, in part, an insert windowcomprising a frame defining an insert window area, a variabletransmittance optical filter suspended within the frame, oversubstantially all the insert window area, and an electrical systemconfigured to receive power from a power source and to provide a voltageto the first and the second electrode of the variable transmittanceoptical filter.

Power from a power source may be received by an electrical system andoptionally stored in an energy storage component, the electrical systemconfigured to deliver power from the energy-harvesting power source,from the energy storage component, or a combination thereof, to the VTOfilter or device to effect a transition of the VTO filter or device froma dark state to a light state, or from a light state to a dark state.The power may be generated by an energy harvesting power source. Theelectrical system may comprise control electronics for controllingaspects such as energy storage, power conversion, and power delivery.The control electronics may be configured to accept input from a user,or from another control system or a sensor.

“Visible light” refers to the band of electro-magnetic radiation with awavelength from about 400 nm to about 750 nm. “Ultraviolet (UV) light”refers to electromagnetic radiation with a wavelength shorter than thatof visible light, or from about 10 nm to about 400 nm range. In someembodiments, sub-ranges of ultraviolet light may be used, and/or mayoverlap with light in the visible range, for example from about 100 toabout 420 nm, or from about 200 to about 420 nm, or from about 300 toabout 420 nm, or from about 350 to about 420 nm. “Infrared radiation(IR)” refers to electromagnetic radiation with a wavelength from about750 nm to about 50,000 nm. Its wavelength is longer than that of visiblelight. Light may also be described with reference to colour or range ofwavelength.

A “light source” is a source of VIS, UV and/or infrared light (IR). Alight source may also provide full spectrum light, including one or moreof VIS, UV and IR light, or light of wavelengths within a VIS, UV or IRrange. Light sources may include natural or simulated sunlight (director indirect), or light from a selected wavelength or range ofwavelengths. The selected wavelength or range of wavelengths may beselected by the nature of the light source itself (e.g. a lamp thatproduces light in a particular range such as a UV lamp, or may beselected through use of a cutoff filter, designed to eliminate lightabove or below a cutoff wavelength, or between two cutoff wavelengths.In some embodiments of the invention, the light source may be configuredto provide light above or below a predetermined wavelength, or mayprovide light within a predetermined range. A device or apparatusaccording to some embodiments of the invention may comprise a lightsource.

Devices according to various embodiments of the invention may bedescribed with reference to clarity, visible light transmittance,switching speed, durability, photostability, contrast ratio, state oflight transmittance (e.g. dark state or light state) to further definethe device, or aspects of the device; some values or characteristics ofsuch descriptors may be applicable to some or all devices, but onlyexemplified in one type of device; alternately, some values orcharacteristics of such descriptors may be applicable to only a fewtypes of devices.

“Visible light transmittance (VLT)” refers to the quantity of visiblelight that is transmitted or passes through an optical filter, film ordevice. VLT may be expressed with reference to a change in lighttransmission and/or a particular type of light or wavelength of light(e.g. from about 10% visible light transmission (VLT) to about 90% VLT,or the like). A product with a higher VLT transmits more visible light.VLT is expressed as a number between 0 and 1, or as a percentage. VLTmay alternately be expressed as absorbance, and may optionally includereference to one or more wavelengths that are absorbed. According tosome embodiments, an optical filter may be selected, or configured tohave in the dark state, a VLT of less than 80%, or less than 70%, orless than 60%, or less than 50%, or less than 40%, or less than 30%, orless than 20% or less than 10%, or any amount or range therebetween.According to some embodiments, an optical filter may be selected, orconfigured to have in the light state, a VLT of greater than 80%, orgreater than 70%, or greater than 60%, or greater than 50%, or greaterthan 40%, or greater than 30%, or greater than 20% or greater than 10%,or any amount or range therebetween. Inclusion of a colourant orcoloured film in the optical filter may additively reduce the VLT of theoptical filter, in combination with the switching material. In someembodiments, the VLT of an optical filter in the dark state or the lightstate may independently be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16,18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 or 95%,or any amount or range therebetween, with the proviso that the darkstate of an optical filter has lesser VLT than the light state of thesame optical filter.

The term “state of visible light transmittance” as used herein, refersto states such as a dark state, or a light state, or transition statesin between. A switching material may darken (e.g. reach a ‘dark state’)when exposed to light (e.g. ultraviolet light) from a light source, orwhen a voltage is applied, and may lighten (“fade”, “electrofade”,“bleach”, “electrobleach”, achieve a ‘light state”) when exposed to anelectric charge, or when exposed to visible light of a selected range.Such a switching material may be alternately described as anauto-darkening material. In some embodiments, the switching material mayfade upon exposure to selected wavelengths of visible (VIS) light(“photofade”, “photobleach”), without sacrifice of the ability to beelectrofaded when restored to a darkened state. This term also refers tostates such as opaque, clear, translucent, or transparent. For example,the term “dark state” can refer to a state in which there is a low to notransmittance of visible light. The term “light state” can refer to astate in which there is a high degree of transmittance of visible light.Dark state and light state may be described relative to each other.

The contrast ratio is a ratio of the VLT of a VTO filter, component ofan optical filter or device comprising an optical filter in the darkstate and the light state. For example, an optical filter may allowtransmission of about 10% of the visible light (˜10% VLT) in a darkstate, and about 60% of the visible light (˜60% VLT) in a faded state,providing a contrast ratio of about 6 (6:1). According to variousembodiments of the invention, a material may have a contrast ratio of atleast about 2, or 3, or 4, or 5, or 6, or 7, or, or 9, or 10, or 11, or12, or any amount or range therebetween. It will be appreciated by thoseskilled in the art that other configurations of % VLT in light and darkstates, and contrast ratios thereof, may be possible with othercompounds, formulations or the like.

Clarity may be affected by haze due to cloudiness caused by scatteringof light. Light may be scattered by particles that are suspended in thesubstance. Haze may be measured by methods known in the art, forexample, using a “hazemeter” (e.g. XL-211 Hazegard, BYK Gardner),according to known and/or standardized methods. Optionally, the haze ofthe optical filters according to various embodiments is between about 0%and about 5%. In some embodiments of the invention, the optical filterhas a haze transmission of about 5% or less, about 3% or less, about 2%or less, about 1.5% or less, or about 1% or less, or from 0-5%, 0.5 to3% or the like.

“Switching time” (“switching speed”) refers to the time necessary for amaterial to transition from a dark state to a clear state, or from aclear state to a dark state, or to alter light transmission by a definedamount (e.g. 60% to 10% VLT in 5 minutes). may depend on theconstruction and components, however, generally the optical filters ofthe present invention will have a darkening time of between about 1second and 30 minutes to reach about 10% of the VLT of the dark statefrom the lightened state, and a lightening time of between about 1second and 30 minutes to reach about 90% of the VLT of the light statefrom the darkened state. In some embodiments of the invention, thedarkening time and lightening time of the optical filter areindependently about 1, 2, 3, 4 or 5 minutes, or any amount of time orrange therebetween.

The term “mil” as used herein, refers to the unit of length for 1/1000of an inch (0.001). One (1) mil is about 25 microns; such dimensions maybe used to describe the thickness of an optical filter or components ofan optical filter, according to some embodiments of the invention. Oneof skill in the art is able to interconvert a dimension in ‘mil’ tomicrons, and vice versa.

As used herein, the term “about” refers to a +/−20% variation from thenominal value. It is to be understood that such a variation is alwaysincluded in a given value provided herein, whether or not it isspecifically referred to.

Variable Transmittance Optical (VTO) Filter

In one embodiment, a VTO filter comprises a first transparent substrate,a conductive layer disposed thereon and a switching material disposedupon the conductive layer. The conductive layer may be continuous, ordiscontinuous. Where the conductive layer is discontinuous, theconductive layer may be configured to comprise two or more electricallyseparated electrodes arranged in a substantially co-planar relationship,such as described in U.S. Patent Application No. 61/423,536 filed Dec.15, 2010, and in PCT Application PCT/CA2011/001378. VTO filters are alsodescribed in PCT Publication WO2010/142019.

In another embodiment, a VTO filter comprises a first transparentsubstrate comprising a first electrode, a second transparent substratecomprising a second electrode, and a switching material disposed betweenand operatively (electrically) coupled to the first and secondelectrodes. The first and second substrates may be rigid or flexible;where the first and second substrates are flexible, the switchingmaterial may also be flexible. The switching material is transitionablefrom a first light transmittance state to a second light transmittancestate with application of a voltage, light from a light source, orapplication of both a voltage and light from a light source.

Referring to FIGS. 1 and 2, a schematic diagram of a cross-section of avariable transmittance optical filter according to some embodiments ofthe invention is shown generally at 20. A schematic diagram of across-section of a curved optical filter according to some embodimentsof the invention is shown generally at 40. A first transparent substrate22 has a first transparent conductive layer 24 disposed thereon, and asecond transparent substrate 26 has a second transparent conductivelayer 28 disposed thereon; a switching material 30 is disposed betweenthe first and second transparent substrates 22, 26 with their respectiveconductive layers 24, 28, and provides the electrical connection betweenthe first and second conductive layers. Electrical connectors 32, 34connect first conductive layer 24 and second conductive layer 28,respectively, via bus bars 36, 38, to a power source where the switchingmaterial 30 is flowable, optional seals 42 may be included to retain theswitching material in the optical filter, between the substrates. Insome embodiments, the seal may prevent ingress of water, gas, oxygen orother material into the switching material, and/or may prevent egress ofone or more components of the switching material. First and secondtransparent conductive layers may be referred to as first and secondelectrodes, respectively. Optional spacer elements may be includedbetween the first and second conductive layers, and may be attached tothe first and/or second conductive layers or first and/or secondsubstrates, or may be free-floating within the switching material.Spacer elements may be glass or plastic beads with a diameter orthickness about the same as the desired gap between the first and secondconductive layers, or first conductive layer and second substrate (foran optical filter with substantially co-planar electrodes). The spacerelements may provide a gap from about 20 microns to about 500 microns,or any amount or range therebetween, for example about 25, 30, 40, 50,60, 70, 80 or 90 microns. The spacer elements, if fixed to a substrateor conductive layer, may be spaced about 0.1 mm to about 1 mm apart, orany amount or range therebetween. Spacer elements may be printed on tothe substrate using a screen printing technique. Spacer elements may beformed of any suitable material, for example acrylic (Electrodag™PD-038, Henkel Corporation, Dusseldorf, Germany). Where the opticalfilter is curved, it may be, for example, a simple curve, a cylindricalcurve, a compound curve, or a spherical curve. The curved optical filtermay be a lens, or comprise a portion of a lens; the lens may becylindrical, spherical, aspherical or the like. The curved opticalfilter may result from bending or flexing a substantially planar opticalfilter comprising flexible substrate(s). In some embodiments, the curvedoptical filter comprises first and optional second substrates that havebeen cast or molded into the selected curved shape, prior to, or after,a transparent conductive layer is applied and/or prior to, or after, aswitching material is applied.

Relative thickness of layers in the figures herein may not represent thetrue relationship in dimensions. For example, where the substrate is arigid pane (e.g. 3, 4, 5 or 6 mm glass of a window), the substrate maybe thicker than the switching material. Where the substrate is aflexible material, the switching material may be thicker than thesubstrate. The figures are drawn for the purpose of illustrating therelationship or connection between components of the device, and not toprovide dimensional information unless otherwise specified.

An electrical connector may comprise a bus bar. A bus bar may be appliedat one edge of the optical filter and be in electrical connection withan electrode of the optical filter. Bus bars are known in the art, andmay be formed of any suitable conducting material (e.g. Cu, Au, Ag or Alfoil, conductive fabric or the like) and affixed to a conductive layerof an electrode using a conducting adhesive material, for example Cutape, polymeric glue or epoxy comprising silver (e.g. Dupont Conductorpaste #4817N), a polymeric glue comprising metal (e.g. Ag, Zn, Fe, Mg,Cu, Al or the like) particles, or the like or may be printed onto asubstrate (e.g. using silver epoxy or silver ink material). US2011/0100709 describes various conducting adhesive mixtures. To affix abus bar, the conductive adhesive is applied to the conductive layer at asuitable location and the conductive material placed on top of theadhesive and pressed to eliminate uncontacted areas, gaps or bubbles.The adhesive is allowed to set or cure as appropriate.

As indicated above, first and second electrodes may be substantiallyco-planar in some embodiments of the invention. For an optical filtercomprising substantially co-planar electrodes, both first and secondelectrodes are disposed on the first transparent substrate, and thesecond transparent substrate may lack a second transparent conductivelayer.

The VTO filter may transition from a first transmittance state to asecond transmittance state upon application of a voltage. The firsttransmittance state may be a dark state and the second transmittancestate may be a light state. The voltage applied may be from about 0.1 Vto about 20 V, or any amount or range therebetween, for example, 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19 V. In someembodiments, the amount of voltage applied is from about 0.1 V to about5V, or from about 1V to about 10 V, or from about 1.0 V to about 2.2 V,or from about 0.5V to about 3V, or from about 1.2V to about 2.5 V, orfrom about 1.8 V to about 2.1 V, or any amount or range therebetween. Insome embodiments, the voltage applied is less than about 12 V, or lessthan about 6 V, or less than about 3 V or less than about 2.5 V, orabout 2 V.

Substrate

In embodiments of the present invention, the transparent substrateprovides sufficient structural integrity to support the switchingmaterial. The substrate may be rigid or flexible. Optical filterscomprising flexible substrate(s) may be in the form of a film that maybe applied to a rigid material, such as a pane of a window, or a lens.In some embodiments, the optical filter may comprise a first substratewith first conductive layer and switching material, and be applied to apane of a window or a lens, the pane or lens comprising a secondconductive layer (the pane or lens being a second substrate). In otherembodiments, the optical filter comprises a first substrate withsubstantially-coplanar electrodes and switching material, and be appliedto a pane of a window or a lens. For such an embodiment, the pane orlens may not include a second conductive layer. Examples of suitablematerials that can be used as a substrate in embodiments of the presentinvention include, but are not limited to, glass, plastics andthermoplastic polymers. Suitable thermoplastic polymers includepolyesters (PE), polycarbonates, polyamides, polyurethanes,polyacrylonitriles, polyacrylacids, (e.g. poly(methacrylic acid),including polyethylene terephthalate (PET), polyolefins (PO) orcopolymers or heteropolymers of any one or more of the above, orcopolymers or blends of any one or more of the above withpoly(siloxane)s, poly(phosphazenes)s, or latex. Examples of polyestersinclude homopolymers or copolymers of aliphatic, semi-aromatic oraromatic monomeric units, for example polycondensed 4-hydroxybenzoicacid and 6-hydroxynapthalene-2-carboxylic acid (VECTRAN™), polyethylenenapthalate (PEN), polytrimethylene terephthalate (PTT), polybutyleneterephthalate (PBT), polyethylene terephthalate (PET),polyhydroxyalkanoate (PHA), polyethylene adipate (PEA), polycaprolactone(PCL) polylactic acid (PLA), polyglycolic acid (PGA) or the like.Examples of polycarbonates include bisphenol A polycarbonate or thelike. Other thermoplastic polymers include polyethene (PE),polypropylene (PP) and the like. For an optical filter or a devicecomprising two or more substrates, the substrates may be the samematerial, or different. The material comprising a substrate may have UV,IR or VIS light blocking characteristics. In one embodiment of theinvention, the substrate material is glass. In one embodiment of theinvention, the substrate material is PET. In one embodiment of theinvention, the substrate is heat-stabilized PET. Suitable glass includesfloat glass, tempered glass, laminated glass, tinted glass, mirroredglass, reinforced glass, safety glass, bullet-resistant glass, “one-way”bullet-resistance glass, Other suitable substrate materials includeceramic spinel or aluminum oxynitride.

In some embodiments, the optical filter, or a device comprising theoptical filter, may comprise one or more UV blocking components (a “UVblocker”) to block some or a substantial amount of the UV light that thedevice of the invention is exposed to in order to counteract UVlight-induced degradation of the switching material. The UV blocker maybe incorporated in the substrate or applied as a layer on a substrate,or applied as a layer of a device according to various embodiments ofthe invention. The layer may be a deposited organic or inorganicmaterial or combination thereof, or may be a film. A UV blocker may bedeposited by any suitable method, for example chemical vapor deposition,physical vapor deposition, (e.g. sputtering, electron beam evaporation,and ion plating), plasma spray techniques, sol-gel processes or thelike. In some embodiments, an adhesive employed to affix an opticalfilter in the form of a film to a pane of a window or a lens may be, orcomprise, a UV blocker (e.g. 8172PCL adhesive from 3M). Examples of UVblockers include WO₂, WO₃, ZnO, CdO or a combination thereof; thin filmmaterials (e.g. a dichroic filter) with thickness and index ofrefraction chosen so as to reflect or absorb UV light; a UV absorbingpolymer or a polymer comprising a light-absorbing or UV stabilizingcomponent. Examples of such polymers include polyethylenes,polypropylenes, polybutylenes, epoxies, acrylics, urethanes, vinylsincluding polyvinyl chloride, poly(vinyl butyral), poly(vinyl alcohol),acetates, polystyrenes, polyimides, polyamides, fluorocarbon polymers,polyesters, polycarbonates, poly(methyl methacrylate), poly(ethylmethacrylate), poly(vinyl acetate), or co-polymers or polymer blendsthereof. In some embodiments, the substrate is PET comprising a UVblocking additive (e.g. XST6578 from DuPont Teijin). Such a substratemay be a UV blocking layer.

In some embodiments, the substrate may have applied to one or both sidesof it a UV, selective UV, IR, selective IR or selective VIS lightblocking layer; the blocking layer may be in the form of a coating orfilm. A selective UV, VIS or IR blocking layer selectively blocks(absorbs or reflects) a portion of UV, VIS or IR light, respectively.Examples of UV blocking films that may be applied include (EnergyFilm™(described in WO2002/018132) and EnerLogic™ (described inWO2009/087575). Examples of UV blocking layers include optical clearpressure sensitive adhesives with UV blocking components (e.g. 8172PCLfrom 3M).

In embodiments of the invention comprising a hybridphotochromic/electrochromic switching material, the concentration of UVlight absorbers in the UV blocking layer and the thickness of the UVblocking layer may be selected so as to provide protection from UVdegradation of the switching material while allowing a sufficientportion of the incident UV light to reach the switching material toeffect auto-darkening. In one embodiment, the UV blocking layer blocksUV light below a certain wavelength. The lower energy UV light can beused to effect the auto-darkening of the switching material. In oneembodiment, the UV blocker blocks most of the UV light below about 350nm, or below about 365 nm, or below about 375 nm, or below about 380 nm,or below about 385 nm. In some embodiments, the VTO filter comprises aswitching material that is transitionable to a dark state when exposedto UV light that is greater than about 350 nm, or greater than about 365nm, or greater than about 375 nm, or greater than about 385 nm, orgreater than about 385 nm.

The substrate material may be of uniform or varying thickness. Thicknessof a substrate may be of any suitable dimension to provide sufficientstructural integrity to support the switching material; determination ofa suitable material and thickness is within the ability of one of skillin the art. For example, the substrate may have a thickness from about0.01 mm to about 10 mm, or any amount or range therebetween, for example0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 mm, or from about 0.012mm to about 10 mm, or from about 0.5 mm to 10 mm, or from about 1 mm to5 mm, or from about 0.024 mm to about 0.6 mm, or from about 0.051 mm (2mil) to about 0.178 mm (7 mil). In some embodiments, the thicknessand/or material of the first substrate differs from the thickness and/ormaterial of the second substrate.

The substrates can optionally include additives or coatings such as abase colour tint or coloured layer to provide a darker overall range orcolour to the optical filter, a barrier coating to block moisture, anantireflective coating and/or, a scratch resistant coating. Apressure-sensitive adhesive coating may be applied for laminating theoptical filter onto glass. In some embodiments, an air gap may beprovided between a substrate layer and an adjacent layer, for example tofacilitate thermal insulation.

Electrodes

The conductive transparent layer(s) may alternately be referred to aselectrode(s). Suitable materials for the conductive layers arewell-known to those skilled in the art and include, for example, metaloxides, graphene, carbon nanotubes, and fine wire meshes. Exemplaryconductive materials include layers of doped indium tin oxide, doped tinoxide, doped zinc oxide, antimony tin oxide, polyaniline, graphene,PEDOT (poly(3,4-ethylenedioxythiophene)), PEDOT:PSS(poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)), andpolypyrrole, as well as thin, substantially transparent metallic layerssuch as gold, silver, aluminum, and nickel alloy. Methods of applyingthe electrically conductive material to a substrate to form suitableconductive layers and electrodes are well known in the art e.g. chemicaldeposition, sputter coating or the like. The conductive layer is coatedor deposited onto the substrate to a thickness that provides adequateconductance for operation of the electrodes, and which does notappreciably interfere with the transmission of light. In one embodiment,the thickness of the conductive layer ranges from about 1 nanometer toabout 90 microns, or any amount or range therebetween. In anotherembodiment, the thickness of the conductive layer ranges from about 10nanometers to about 10 microns, or any amount or range therebetween.

In one embodiment of the invention, the conductive transparent layer(s)of the substrate material has a sheet resistance of up to about 100Ohms/square, or up to about 1000 Ohms/square, or up to about 100,000Ohms/square or up to about 1,000,000 Ohms/square, or any amount or rangetherebetween. In some embodiments of the invention, the transparentconductive material may have a sheet resistance from about 10Ohms/square to about 1000 Ohms/square; or from about 20 Ohms/square toabout 500 Ohms/square; or from about 100 Ohms/square to about 1,000Ohms/square; or from about 1,000 Ohms/square to about 10,000Ohms/square; or from about 10,000 Ohms/square to about 1,000,000Ohms/square; or from about 1,000,000 Ohms/square to about 5,000,000Ohms/square; or from about 5,000,000 to about 10,000,000 Ohms/square; orany amount or range therebetween.

Substrate materials pre-coated with indium tin oxide (ITO) are availablefrom a number of suppliers, including CP Films of St. Louis, Mo. andSouthwall Technologies Inc. of Palo Alto, Calif. One skilled in the artwill recognize that multiple layers of conductive materials can also beemployed in embodiments of the present invention.

Switching Material

A switching material (“transition material”) reversibly interconvertsbetween a first state of light transmittance and a second state of lighttransmittance and may be may be electrochromic, photochromic,thermochromic, or a combination thereof. Application of a firststimulus—voltage, light or temperature, respectively changes the colouror alters VLT of the material. In some embodiments, the change in colouror VLT may be reversible with application of a second stimulus; thesecond stimulus may be a voltage, a light or a temperature stimulus.

In some aspects of the invention, the switching material may be anelectrochromic or another material such as liquid crystal, materialsforming a suspended particle device, or other present or futureswitching materials as would be readily understood by a worker skilledin the art. Electrochromic materials include tungsten oxide,polyaniline, viologens, polyoxotungstates or the like. Electrochromicmaterials can be used to dynamically alter the visible lighttransmission properties of a material through the application ofelectricity. Electrochromic technology typically involves applying thincoatings of electrochromic materials to two transparent electrodes andsandwiching an electrolyte material in between. Unlike photochromictechnology, electrochromic technology typically requires externalelectrical power to darken (see for example U.S. Pat. No. 6,934,067,describing an electrochromic rear view mirror. Liquid crystal filterscomprise a liquid crystal material between two transparent electrodes.When an electric field is applied between the electrodes, the liquidcrystals align in a certain orientation to allow light to pass throughthe filter. In the absence of a field, the liquid crystals have a randomorientation and scatter the light, appearing translucent to an observer(see, for example U.S. Pat. No. 7,459,189 and U.S. Pat. No. 7,300,167.Suspended Particle Devices or displays (SPD) involve many smallparticles suspended in a liquid between two sheets of glass withconducting electrodes. Like liquid crystals, a voltage applied acrossthe electrodes causes the particles to align and light is transmitted.In the absence of a voltage, the particles are randomly distributed andscatter light. The scattering of light means that SPD devices aretypically not optically clear in the dark state. See, for example U.S.Pat. No. 5,463,491 and U.S. Pat. No. 6,910,729.

In some embodiments, the switching material comprises a compound that iselectrochromic and photochromic (a “hybrid P/E” compound). A switchingmaterial comprising a hybrid P/E compound (hybrid P/E switchingmaterial) may darken (e.g. reach a ‘dark state’) when exposed to lightcomprising UV wavelengths, and may lighten (“fade”, “electrofade”,“bleach”, “electrobleach”, achieve a ‘light state”) when exposed to anelectric charge via application of a voltage. Such a switching materialmay be alternately described as an auto-darkening material. In someembodiments, the switching material may fade upon exposure to selectedwavelengths of visible (VIS) light (“photofade”, “photobleach”), withoutsacrifice of the ability to be electrofaded when restored to a darkenedstate. In some embodiments, the hybrid P/E compound is a single organicspecies having both photochromic and electrochromic isoforms and isreversibly interconvertible between isoforms with application of lightand/or voltage, respectively. In some embodiments, the switchingmaterial is a hybrid P/E switching material and is a liquid, a solid, asemi-solid, a sol-gel or a gel. The liquid, sol-gel or gel may be of arange of viscosity.

The thickness of the layer of hybrid P/E switching material may affectthe transmittance of the variable transmittance optical filter of theinvention and may be selected depending on the particular applicationdesired. For example, when comparing a thinner and a thicker layer ofthe same hybrid P/E switching material, the thicker layer may provide alower percentage visible light transmission in the dark state. Kineticsof the reduction and oxidation reactions may also be affected by thethickness of the switching material, a thinner layer may demonstrate afaster fading time than a thicker layer. In some embodiments of theinvention, the hybrid P/E switching material has a thickness from about0.1 microns to about 10,000 microns; or from about 1 to about 1000microns; or from about 10 microns to 100 microns, or any amount or rangetherebetween for example 15, 20, 30, 40, 50, 60, 70, 80 or 90 microns.Typically, uniform thickness of the hybrid P/E switching material willbe desired in most applications; however, it is contemplated that avariable transmittance optical filter of the invention can comprise anon-uniform thickness of the hybrid P/E switching material forapplications where some darker regions and some lighter regions aredesired.

In some embodiments, the switching material is a hybrid P/E switchingmaterial comprising one or more organic, hybrid P/E compounds. Incertain embodiments, the hybrid P/E switching material may comprise oneor more optional components. For example, the hybrid P/E switchingmaterial may further comprise one or more of a solvent, an electrolyte,a polymer, a charge compensator, a charge carrier, a UV stabilizingagent, a UV blocking agent, a tinting agent, or the like. One skilled inthe art will recognize that certain components may be able to fill dualroles in the hybrid P/E switching material, for example, certain dyesmay self-polymerize and fulfill the role of both dye and polymer;certain polymers may also have UV blocking capabilities; or the like.Conversely, in some embodiments, a given component may be made up ofseveral individual compounds, e.g., the polymer component may be acopolymer comprising different monomeric units.

In one embodiment, the hybrid P/E switching material of the inventioncomprises a hybrid P/E compound and a component in which the hybrid P/Ecompound is soluble such as a solvent or a polymer, or a polymer thatfulfills the function of a solvent. In another embodiment, the hybridP/E switching material of the invention comprises a hybrid P/E compound,a solvent, and at least one optional component selected from the groupconsisting of: a) an electrolyte; b) a polymer component; c) a chargecompensator; d) a charge carrier; e) a UV stabilizing agent; f) a UVblocking agent; and g) a tinting agent. In some embodiments, the hybridP/E compound or hybrid P/E switching material is transitionable from alight state to a dark state when exposed to UV light that is greaterthan about 350 nm, or greater than about 365 nm, or greater than about375 nm, or greater than about 385 nm, or greater than about 385 nm. Insome embodiments, the hybrid P/E compound or hybrid P/E switchingmaterial that is transitionable to a dark state when exposed to UV ofabout 350 to about 420 nm, or of about 365 to about 420 nm, or of about375 to about 420 nm, or of about 380 nm to about 420 nm, or of about 385nm to about 420 nm.

Hybrid P/E Compounds:

The hybrid P/E switching material according to some embodimentscomprises one or more organic compounds (“dyes” or “chromophores”) thatexhibit both photochromic and electrochromic characteristics. These dualmode compounds are capable of reversibly switching between two distinctisoforms when stimulated electrically and by light. The hybrid P/Ecompounds are organic, and include classes of compounds from thehexatriene family, for example, the class of compounds known in the artas diarylethenes, dithienylcyclopentenes, and fulgides. In someembodiments, conversion of the compound to the ring-open form is inducedby application of a voltage to a switching material comprising thecompound, and is independent of the polarity of the applied voltage.

According to one embodiment of the invention, the hybrid P/E switchingmaterial comprises one or more chromophores from the class of compoundsknown as diarylethenes. Examples of diarylethenes include derivatives of1,2-dithienylcyclopentene as described in International PatentPublication No. WO 2004/1015024, having the general structure of Formula1 below:

wherein each R₁ is independently H or a halogen;Z is N, O or S;wherein each R₂ is independently H, a halogen, or both R₂ when takentogether form CH═CH, or when in polymeric form R₂ is CH═CH and formspart of a polymer backbone;wherein each R₃ is independently alkyl, aryl, H, a halogen or CO₂Y (Y═H,Na, alkyl, aryl);wherein R₄ is aryl; andwherein each R₅ is independently H, alkyl or aryl.“Aryl” includes substituted or unsubstituted benzyl or thiophenyl.Substitutions may be alkyl, halogen or the like. Benzyl may besubstituted in ortho, meta or para positions of the benzyl ring.Thiophenyl may be substituted at one or more of positions 2, 3, 4 or 5of the thiophene ring.“Halogen” includes F, Br and Cl.“Alkyl” includes methyl, ethyl, propyl, butyl, t-butyl.

Preparation of exemplary fluorinated dithienylcyclopentene derivativesthat may be incorporated in the switching materials of the inventionfollows the general methodology of Scheme 1 below:

In one embodiment of the invention, the switching material comprisescompounds of Formula 1 wherein R₁ and R₂ are F, R₃ and R₄ are

(X═S), and R₅ is H. In another embodiment of the invention, theswitching material comprises compounds of Formula 1 wherein R₁ and R₂are F, R₃ is H, R₄ is

(X═S), and R₅ is H. In a further embodiment of the invention, theswitching material comprises compounds of Formula 1 wherein R₁ and R₂are F, R₃ and R₄ are independently

or

and R₅ is H. In a further embodiment of the invention, theswitching material comprises compounds of Formula 1 wherein R₁ and R₂are F, R₃ is

(X═S), R₄ is CH₃, and R₅ is H. In another embodiment of the invention,the switchingmaterial comprises compounds of Formula 1 wherein R₁ and R₂ are F, R₃ is

(X═S); R₄ is CH₃, and R₅ is H.

The chromophores can be incorporated into the switching material inmonomeric or polymeric forms depending on the functional demandsrequired. The compounds of Formula 1 may be incorporated in polymericform as part of the polymer backbone or as a pendant group. For example,fluorinated compounds may be polymerized using ring-opening metathesispolymerization in accordance with Scheme 2 below:

Exemplary non-fluorinated dithienylalkene derivatives that may beincorporated in the switching materials of the invention can be preparedin accordance with the general methodology of Scheme 3 below:

In one embodiment of the invention, the switching material comprises acompound of Formula 1 wherein R₁ is H, R₂ is CH═CH, R₃ is Cl, R₄ is CH₃,and R₅ is H. In another embodiment of the invention, the switchingmaterial comprises a compound of Formula 1 wherein R₁ is H, R₂ is CH═CH,R₃ is CO₂CH₃, R₄ is CH₃, and R₅ is H. In a further embodiment of theinvention, the switching material comprises a compound of Formula 1wherein R₁ is H, R₂ is CH═CH, R₃ is

(X═S), R₄ is CH₃, and R₅ is H.

In other embodiments of the invention, the switching material comprisesa compound of Formula 1 wherein the compound forms part of a polymer. Inone embodiment of the invention, R₁ is H, R₂ is CH═CH and forms part ofthe polymer backbone, R₃ is Cl, R₄ is CH₃, and R₅ is H. In a furtherembodiment of the invention, the switching material comprises a compoundof Formula 1 wherein R₁ is H, R₂ is CH═CH and forms part of the polymerbackbone, R₃ is CO₂CH₃, R₄ is CH₃, and R₅ is H. In another embodiment ofthe invention, the switching material comprises a compound of Formula 1wherein R₁ is H, R₂ is CH═CH and forms part of the polymer backbone, R₃is CO₂H, R₄ is CH₃, and R₅ is H. In another embodiment of the invention,the switching material comprises a compound of Formula 1 wherein R₁ isH, R₂ is CH═CH and forms part of the polymer backbone, R₃ is

(X═S), R₄ is CH₃, and R₅ is H.

An example of a suitable chromophore for inclusion in the hybrid P/Eswitching material is one that exhibits both photostability as well aselectrochemical durability. The photostability of a compound, e.g., theresistance of the chromophore to light induced degradation, can bemeasured by the amount of time it takes for the compound to degrade to acertain point under constant light exposure. For example, in oneembodiment the compound can be measured in its dark state and its lightstate to determine its contrast ratio prior to testing. During testing,the contrast ratio is monitored periodically to determine degradation.Failure can be determined to occur when the contrast ratio falls below acertain level, or when the contrast ratio falls below 50% of theoriginal contrast ratio. Other methods for testing are within theknowledge of persons skilled in the art. The photostability ofembodiments of the invention can be tested using a QUV or QSUN testingunit made by Q-Lab of Cleveland, Ohio. In one embodiment, the hybrid P/Eswitching material of the invention comprises a chromophore having aphotostability in the range of about 1000 hours to about 5000 hours, orover 5,000 hours of constant light exposure. The electrochemicaldurability of a suitable chromophore is measured as the number of cyclesthat the chromophore can maintain its switching activity between thelight and dark state. In one embodiment, the hybrid P/E switchingmaterial of the invention comprises a chromophore having anelectrochemical durability in the range of about 1000 to about 5,000cycles or over 5,000 cycles. Typically, the hybrid P/E switchingmaterial according to the present invention contains (by weight) 0.05%to about 30%, or any amount or range therebetween, for example about 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28 or 29%.

Examples of selected hybrid P/E compounds include: S001, S002, S042,S054 and S068; or derivatives thereof having different functional groupsof the peripheral benzyl or thiophene rings.

Solvent:

The solvent component of the hybrid P/E switching material dissolves,intersperses and/or diffuses the one or more chromophores and othercomponents throughout the hybrid P/E switching material. The solventused in the preparation of the switching material is typically inert,e.g., photochemically and electrochemically inactive, and colourless,and has a sufficiently high boiling point to prevent solvent loss undertypical operating conditions Examples of suitable solvents include, butare not limited to, triglyme, dichloroethane, tetraglyme, propylenecarbonate, ethylene carbonate, water, butyrolactone, cyclopentanone andmixtures thereof. In one embodiment of the present invention, thesolvent component comprises triglyme.

One or more solvents may be present in a switching material in an amountfrom about 50% to about 95% (by weight), or any amount or rangetherebetween, for example 50, 60, 70, 80 or 90%, or any amount or rangetherebetween.

Electrolyte:

Electrolytes are generally electrically conductive, and may includealkali metal salts, tetralkylammonium salts or the like. Examples ofelectrolytes include TBABF₄ (tetrabutylammonium tetrafluoroborate),TBAPF₆ (tetrabutylammonium hexafluorophosphate), tetrabutylammoniumperchlorate, lithium bis(trifluoromethane sulfonimide), lithiumtriflate, LiBOB (lithium bis(oxatlato)borate), LiClO₄ (lithiumperchlorate) or the like. The one or more electrolytes may be present inan amount from about 0.1% to about 10% (by weight) or any amount orrange therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, or 9%.

Polymer Component:

In some embodiments of the invention, one or more polymers or sol-gelsmay be included in the compositions. Examples of polymers includepolyvinylbutyral (PVB) B-90, PVB-B72, poly(methyl methacrylate) (PMMA),nitrile rubber (NBR), polyvinylpyrrolidone (PVP), polyvinylidenefluoride (PVDF), poly(dimethylsiloxane) (PDMS), poly(ethyl methacrylate)(PEMA), The one or more polymers or sol-gels may be present in an amountfrom about 0.1% to about 30% (by weight) or any amount or rangetherebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18,20, 22, 24, 26, 28 or 30%, or any amount or range therebetween. In someembodiments the one or more polymers or sol-gels may function as arheology modifier.

Charge Compensator:

In some embodiments of the invention, a charge compensator(charge-transfer complex or charge-transfer salt) may be included in oneor more compositions. A charge compensator may be a cathodic material toaid in redox balance of an anodic chromophore. The charge compensatormay be stable, or sufficiently stable in both reduced and oxidizedforms. The charge compensator may be an organic semiconductor. Examplesof charge compensators include Prussian Blue (PB), ferroceniumtetrafluoroborate, ferrocenium hexafluorophosphate,tetracyanoquinodimethane, tetrafluoro-tetracyanoquinodimethane,1,4-dicyanobenzene, 1,2,4,5-tetracyanobenaene, pyrene, tetracene,pentacene or the like. The one or more charge compensators may bepresent in an amount from about 0.1% to about 10% (by weight) or anyamount or range therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, or 9%

Charge Carrier:

The primary role of the charge carrier component is to facilitatetransport of the electrons and “holes” between the two electrodes andconsists of, or any combination of, substances known in the art to besuitable charge carrier materials. The charge carrier used in thepreparation of the hybrid P/E switching material is typically redoxactive in the electrochemical potential range required to trigger colourlightening of the hybrid P/E switching material. Examples of suitablecharge carriers include, but are not limited totris(4-bromophenyl)amine, tris(4-chlorophenyl)amine, 10-methylphenothiazine, 9,9-(N,N,N′,N′-tetrabiphenyl-N,N′-diphenyl)fluorene,4,4′-di(N-carbozolyl)biphenyl, 1-(N-carbozolyl)-4-diphenylaminobenzene,N,N,N′N′-tetraphenylbenzidine, and1-(N-Carbozolyl-4-N′-alpha-naphthyl-N′-phenylamine. The hybrid P/Eswitching material according to the present invention typically containsabout 0.1% to about 10% by weight of the charge carrier component

UV Stabilizer:

The primary role of the UV stabilizer is to inhibit photodegradation ofthe hybrid P/E switching material by scavenging radical intermediatesformed in photodecomposition processes and consists of, or anycombination of, substances known in the art to be suitable UVstabilizing materials. Examples of suitable UV stabilizers include, butare not limited to the class of compounds known in the art as hinderedamine light stabilizers (HALS). One or more UV stabilizers may bepresent in an amount from about 0.01% to about 10% (by weight) or anyamount or range therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, 9 or10%.

UV Blocker:

The primary role of the UV blocker (or UV absorber) is to preventphotodegradation of the auto-darkening material by including a componentof the material that absorbs higher energy UV light and dissipates theenergy thermally preventing photodecomposition and consists of, or anycombination of, substances known in the art to be suitable UV blockingmaterials. Examples of suitable UV blockers include, but are not limitedto benzotriazoles, benzophenones. One or more UV absorbers may bepresent in an amount from about 0.01% to about 10% (by weight) or anyamount or range therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, or 9%.

Tinting Agent:

Inclusion of a colourant or tinting agent in a composition according tovarious embodiments of the invention may achieve a desired colour and/oradjust the visible light transmission of the composition. A variety ofcolourants are known in the art, and selection of a colourant to achievea desired colour, hue or transmissibility is within the ability of askilled worker. Examples of colourants include one or more chromophoresas described herein, Prussian blue, or the like. One or more colourantsmay be present in an amount from about 0.01% to about 10% (by weight) orany amount or range therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, or9%

Although the optional components noted above have been described withreference to the hybrid P/E switching material, one of skill in the artwould understand that some of these optional components could also beused when the variable transmittance optical filter comprises aswitching material other than a hybrid P/E switching material.

Preparing the Optical Filter

Optical filters may be prepared by any of several methods, includingpressing, knife coating, roll-to-roll processes, or similar methods thatenable application of switching material to be applied to a substrate. Amethod for making a flexible VTO filter generally comprises the steps ofproviding a first flexible transparent substrate, having a transparentconductive material coated or deposited on one side of the flexibletransparent substrate to form at least one electrode, and coating ordepositing the conductive side of the flexible substrate with aswitching material. The method may further comprise a step of providinga second flexible substrate, and applying the second flexible substrateon top of the switching material to form a sandwich structure with theswitching material in contact with the two transparent conductiveelectrodes. For an embodiment where the first flexible substratecomprises both first and second electrodes, the second flexiblesubstrate need not comprise a conductive layer. For embodiments wherethe first flexible substrate comprises one electrode, the secondflexible substrate may further comprise a conductive layer.

In some embodiments, a method of making an optical filter comprisesproviding a first transparent substrate, applying a substantiallytransparent conductive coating to one side of the transparent substratein order to form an electrode, coating the substrate with a switchingmaterial, and laminating a second similarly prepared second transparentsubstrate coated with a conductive coating on top of the switchingmaterial to form a ‘sandwich’ structure, the switching material betweenthe conductive coatings of the first and second substrates.

In one embodiment, the switching material is a fluid having a highviscosity at room temperature and may be made into a lower-viscosityliquid by heating to allow it to be applied or coated onto thesubstrates. In one embodiment, the switching material is heated to about100° C. and pressed between the substrates. The switching material maycomprise a co-solvent and may becast as a liquid (e.g. wet-coating forroll-to-roll methods), and further treated to remove the co-solvent andto increase the viscosity of the switching material. For example, theswitching material can be dried (evaporating the solvent or co-solvent)ors cured to increase the viscosity to form a gel, semi-solid or solid.Curing the switching material may be accomplished with UV light, heat ora combination thereof. A photoinitiator may be added to the switchingmaterial which, when exposed to UV light, can help to cross-link theformulation to increase its viscosity. Other methods of curing such asexposure to electron beams may be possible with different formulations.One skilled in the art will appreciate that this polymerization and/orcross-linking can be initiated by chemical-, thermal-, or photo-typeinitiators. A common method of UV curing can be accomplished by adding aconstituent that, when exposed to UV light, will form a radical toinitiate polymerization and/or cross-linking. Suitable polymerizationinitiators are known in the art and include, for example, heat sensitiveinitiators such as AIBN, photoinitiators such as DAROCUR™ 4265. Thegelled switching material can then adhere to both substrates to form anintegral structure.

Once the filter has been made, it can be cut to size and/or sealedaround the perimeter, and an electrical connection can be made to theelectrodes. Bus bars and/or connectors may be placed before or aftercutting and/or sealing. The electrical connection can be made byprinting bus bars onto the substrates in contact with the transparentconductive coating; alternately, bus bars may be affixed with aconductive adhesive. Electrical leads can then be attached to the busbars, and connected to the electrical control system and/or energyharvesting power source and/or power storage device. The optical filterwhen completed will darken automatically in the presence of UV light andallow the user to return it to a lighter state when an appropriateelectrical charge is applied to the electrodes.

Power Source and Energy Storage Components

Devices according to various embodiments of the invention may comprise apower source. Examples of power sources include batteries, and energyharvesting power sources. In some embodiments, the device is a windowsuch as an insert window, and the power source may be one or morebatteries; the window may optionally be electrically connected to abuilding electrical system. An electrical connection to a buildingelectrical system may be advantageous for a window according to variousembodiments of the invention, as the window may continue to be operablein the event that the one or more batteries fail to supply sufficientpower. In some embodiments, the window may comprise an energy harvestingpower source that provides sufficient power to operate the window,and/or provide power for recharging an energy storage component.

The term “energy-harvesting” (“power harvesting” or “power scavenging”)is used to refer to components that capture energy from externalavailable sources. As used herein, energy-harvesting technology includessolar cells, solar panels, or other photovoltaics, vibrationalenergy-harvesting technologies such as piezoelectrics, acousticconverters, or other mechanical energy converters, and thermalenergy-harvesting technologies such as pyroelectrics andthermoelectrics. Energy-harvesting may include but is not limited tolow-power energy-harvesting. Harvested energy may be stored in an energystorage component, and the electricity used provide power to a device orsystem according to various embodiments of the invention, by applicationof a voltage across the first and second electrodes of the device.

Referring to FIGS. 3A and 3B, a flexible self-powered variabletransmittance optical device according to an embodiment of the inventionis shown generally at 70. FIG. 3B is an enlarged view of the circledregion of FIG. 3A. In some embodiments the device may be a film that maybe applied to an existing window, a pane for use in a window, anopthalmic device, or a lens or visor for use in an opthalmic device. Thedevice comprises a flexible optical filter 72. The device furthercomprises a user interface portion 74 with membrane switches 76,electrical system 78 operatively coupled to the user interface 74 byconnectors (not shown). Electrical system 78 may comprise controlcircuitry, power management circuitry, optional display 79 for providinginformation relating to various parameters of the device such as VLT,applied voltage, voltage stored in the energy storage device, userinstructions or the like, or other components for operation of thedevice. Electrical system 78 is operatively coupled to the first andsecond electrodes by connectors 84, 85 of the device for application ofvoltage thereto, and to one or more optional energy storage components80 by connector 81. Energy harvesting power source 82 is operativelycoupled to electrical system 78 by connector 83. Some or all of the userinterface, the electrical system, the energy storage components, or theenergy-harvesting power source, may be formed at least in part offlexible materials, such as flexible conductors, films, coatings or thelike, thereby facilitating flexibility of the device. Alternatively someor all of these components may comprise a smaller, inflexible portion ofthe device, thereby facilitating flexibility of a substantial portion ofthe device. Components disposed on the device may be configured to havea low profile, thereby facilitating a thinner device.

Power for the voltage applied to the optical filter may be supplied byan energy-harvesting power source (EHPS). Devices in accordance with thepresent invention comprise one or more EHPS for generating power. Theterm “energy-harvesting” is used to refer to components that captureenergy from an external source. Energy-harvesting power sources includephotovoltaic power sources (e.g. solar cells, solar panels, or arraysthereof, photoelectric cells or arrays and the like); piezoelectricpower sources; electrostatic (capacitive) power sources; pyroelectricpower sources, thermoelectric power sources; or the like. EHPS may alsoinclude, or be described as, renewable power sources, or ‘green’ powersources. Energy harvesting may include but is not limited to low-powerenergy harvesting, for example energy harvesting of less than 20 W, lessthan 10 W, less than 5 W, less than 2 W or less than 1 W, In someembodiments, low-power energy harvesting may be from about 0.001 toabout 20 W, or from about 0.001 to about 1, or from about 0.005 to about2, or from about 1 to about 5, or from about 2.5 to about 20 or fromabout 5 to about 20 W, or any amount or range therebetween, The power isused at least in part for application of a voltage for transitioning theswitching material of the optical filter. The power may also be used foroperating aspects of the electrical system, such as control or userinterface components. Inclusion of an EHPS in a device facilitatesself-powering of the device according to various embodiments of theinvention. Advantages of self-powered devices may include one or moreof: reduction or elimination of the need to run power lines to devices:reduction or elimination of maintenance programs to recharge or replacebatteries; increased portability of devices for increased periods oftime; independence from centralized power sources, or the like, or acombination thereof. Installation of a self-powered device that uses arenewable energy source may provide societal, business and/or financialbenefits to a user, through installation and/or use of a ‘green’ powersource.

The EHPS may be a photovoltaic energy-harvesting power source (PV-EHPS).An example of a suitable PV-EHPS may be Sanyo Am-5608 (5v, 17.8mA-60.1×41.3 mm; available from Digikey). A small photovoltaic powersource can be incorporated into a portion of the self-powered device,for example in a corner of a smart window in or on a variabletransmittance optical filter, or applied to the frame of the window orother device. The photovoltaic power source may be sized to provideadequate power for a predetermined level of operation of the device,while remaining relatively inconspicuous and positioned for adequateexposure to a light source. Components of a PV-EHPS may be transparent,semi-transparent or opaque. Flexible PV-EHPS, and flexible electricalsystem components will be known to those of skill in the art, and may beused in embodiments of the invention if desired. A vibrationalenergy-harvesting power source may be an acoustic power source, oranother power source configured to convert mechanical energy intoelectrical power. A piezoelectric power source may be used to transformambient vibrations into electrical energy; see, for example U.S. Pat.No. 7,385,333, U.S. Pat. No. 6,984,902, U.S. Pat. No. 8,030,807, US2010/0072759. Vibrational energy may be a readily available source ofpower for wearable devices (e.g. opthalmic devices) or for windows,since these may provide a large and readily available surface forreceiving vibrations. A variable transmittance optical device accordingto some embodiments of the invention, capable of converting sufficientacoustic energy may further provide a noise dampening effect, which mayreduce street noise, for example.

In some embodiments, the EHPS of a device may comprise a thermal EHPSsuch as pyroelectric power source or thermoelectric power source.Exterior windows form a boundary between building or vehicle interiorand exterior and thus provide a thermal gradient (either the interior orexterior may be of the higher temperature, depending on the climate andenvironmental conditions), allowing exploitation of the thermoelectriceffect to generate an electric voltage. Other thermal energy sourcesinclude a user's body heat, which may be useful for powering wearabledevices such as ophthalmic devices, since these may be placed in contactwith a user to draw body heat therefrom. Thermoelectric generators areknown in the art, see, for example US2008/0066796, US7397169, US2011/0215590.

The energy-harvesting power source may be supplemented or replaced withconventional power sources, such as power from an electrical outlet. Forexample the device may be configured for operatively coupling tobuilding AC power via an AC/DC convertor, or vehicle battery power, orthe like, which can be plugged in as needed to charge the energy storagecomponent. In some embodiments, the control circuit comprises an AC/DCconvertor. The energy-harvesting power source may be disposed on one ormore selected surfaces of the one or more transparent substrates, or itmay be disposed adjacent to the transparent substrates. For example, asolar cell or array thereof may be disposed on either side of either ofthe first or second transparent substrates, or at a plurality oflocations. This may provide for additional flexibility in configurationof the present invention, to appropriately place the energy-harvestingpower source for collection of energy. In some embodiments, if theswitching material is disposed between a light source and a solar cellor array thereof, the switching material may, in a darkened state,inhibit or reduce powering of the solar cell, depending on itstransmittivity characteristics to wavelengths of light converted topower by the solar cell. However, in such cases, an energy storagecomponent may be used to facilitate switching of the switching material.

An electrical system receiving power from the EHPS may further comprisean energy storage device, capable of storing power generated by theEHPS. Examples of energy storage components include a capacitor, batteryor super capacitor. The energy storage device may be charged by acharger, the charger and/or energy storage device receiving energy fromthe EHPS. Examples of chargers include a trickle charger or a floatcharger, The charger may comprise, or be operatively connected to, oneor more of a charge regulator (e.g. battery regulator), a timer, or avoltage detector, that detects when the energy storage device is at ornear a maximum charge capacity, and automatically ceases to charge theenergy storage device further, until or unless its stored energydecreases.

Use of an energy storage component in conjunction with an EHPS mayfacilitate operation of the device when adequate energy is not availablefrom the EHPS, for example when the device does not receive sufficientlight, or light of suitable wavelengths if a photovoltaic power sourceis used (e.g. the sun isn't out, or the photovoltaic power source ispartially obscured). An energy storage component may additionally, oralternatively, facilitate operation of the device when the power sourcedoes not provide sufficient power relative to that required forswitching of the optical filter. For example, the energy storagecomponent can be used to accumulate and store energy provided from thepower source for intermittent operation of the optical filter.

In operation, where the EHPS is a photovoltaic device, incident light onthe solar cell provides power that may be applied to the device to fadethe switching material from dark to light state and also to charge anoptional energy storage component. Additionally or alternatively, powerfrom the solar cell may be used to recharge the energy storage componentrelatively quickly so that the energy storage component may providesufficient power for operating the switching material from dark to lightstate. Where the incident light on the device comprises a UV portion, ahybrid P/E switching material will proceed to darken; power from thesolar cell and/or energy storage component may be applied to the deviceto inhibit such a transition. The energy storage component may be of asuitable capacity to effect at least a one-time transition of theswitching material from dark to light state after incident light (e.g.interior light or sunlight). In other embodiments, the device comprisinga hybrid P/E switching material may receive sufficient power from theEHPS without the need for an energy storage component in the electricalsystem.

Electrical System

Embodiments of the present invention comprise an electrical systemconfigured to receive power from the energy-harvesting power source andto provide power to the first electrode and the second electrode forapplication of the electric voltage. The electrical system isoperatively coupled to the energy-harvesting power source and to thefirst and second electrodes, and is configured to provide controllableapplication of appropriate amounts of voltage to the electrodes fortransitioning the switching material. The electrical system may compriseone or more energy storage components, voltage regulators, voltagetransformers, current regulators, current transformers, voltagemodulators, current modulators, sensing components, control system,feedback systems, communication electronics, microelectronics, voltageor current-controlled transistors, switches or relays, a charger, acharge regulator, user output interfaces such as annunciators, userinput interfaces such as one or more push-buttons, membrane switches,capacitive touch pad or surface, mechanical switches, or the like; andconnectors electrically connecting the one or more components.Connectors (electrical connectors) may include wires, cables, bus bars,leads, conductive traces or the like, connectors may be etched onto aboard or wafer, or other support housing an EHPS and/or components ofthe electrical system. The electrical system may be provided on aflexible circuit which may be applied to or incorporated into devices orfilters according to various embodiments of the invention. Components ofthe electrical system may have power needs supplied by the EHPS, energystorage components or other power source. The electrical system maycomprise one or more sensors (e.g. light sensors, irradiance sensors, UVsensors, temperature sensors, current or voltage sensors or the like)coupled to and in communication with control electronics. Input from asensor, switch, user interface or the like may be received by thecontrol unit (control system).

The electrical system operatively couples components of the one or moreenergy harvesting power sources in series, in parallel, or a combinationthereof. The operative coupling to the power sources and/or energystorage components may be configured to provide for a predeterminedlevel of voltage and current as required by the electrical system foroperation of the variable transmittance optical device. For example, anarray of n solar cells may be coupled in series to provide power at avoltage which is substantially n times the voltage provided by eachsolar cell individually. As a further example, m banks of sucharrangements of solar cells may be coupled in parallel to provide powerat a current which is substantially m times the current provided by eachbank individually. Other arrangements of conductors for receiving powerfrom the energy-harvesting power source or sources may be provided aswould be readily understood by a worker skilled in the art. In someembodiments, a PV-EHPS may comprise such an array of cells, alternatelyreferred to as a photovoltaic array.

The energy storage component may function to accumulate and storesufficient amounts of energy to facilitate operating the switchingmaterial. The energy storage component may provide some or all of thepower for operating the switching material at a given time. The energystorage component may be configured to store enough energy for operatingthe full area of hybrid switching material of the device from a darkstate to a light state a single time, or a predetermined number oftimes, before needing to be recharged. The energy storage component maybe recharged between, or in some embodiments during, switching events.In further embodiments, such an energy storage component may be used inconjunction with a photovoltaic power source which provides sufficientpower to operate the full area of hybrid switching material of thedevice from dark to light state when light is available for conversionto electricity by the photovoltaic power source.

Referring to FIG. 4A, an electrical system according to variousembodiments of the invention is shown generally at 90. Anenergy-harvesting power source 92 is operatively coupled to componentsof the electrical system by connectors 58 and configured to charge acapacitor or super capacitor 93. A switch 95, when closed, applies powerfrom the power source 92 and/or capacitor 93 to input terminals ofoptional power converter 96. Switch 95 may be directly operable by auser, or it may be operable via a control system by closing and/oropening the switch in response to predetermined conditions (e.g. userinput, sensor feedback, timer operation or the like). For example,switch 95 may be closed upon operation of a pushbutton by a user, andthen opened again upon expiry of a timer, the timer set to expire aftera period of time from switch closing corresponding to the time requiredto transition the optical filter from a dark state to a light state.Power converter 96 may comprise a voltage regulator, a voltageconverter, a current converter, a waveform generator, or the like, or acombination thereof, to convert voltage and/or current supplied by thepower source 92 and/or capacitor 93 to a form and level appropriate forsupplying to the first and second electrodes of the optical filter 70via bus bars 97 and 98 and connectors 84 and 85.

Referring to FIG. 4B, an electrical system according to variousembodiments of the invention is shown generally at 91. Power source 92is operatively coupled to the electrical system by connectors 58 andconfigured to directly supply power to the electrical system and/orcharge an energy storage component 94. Optional charge controller 99 maybe provided to control charging of the energy storage component 94.Switching system 95 a comprises one or more switches for controllablycoupling the power source 92 and/or the energy storage component 94 withthe optional power converter 96, providing power to first and secondelectrodes of the optical filter 70 via busbars 97 and 98 and connectors84 and 85. Switches of the switching system 95 may be of any suitableform, and may be connected in series, parallel, or a combinationthereof, and optionally in one or more feedback loops, and may beoperatively interconnected with each other and/or with control system101.

In one embodiment, the switching system 95 a comprises a first switchwhich may be closed by operation of the control system 101 to providepower from the power source 92 to power converter 96, configured toapply an appropriate voltage and/or current to the electrodes. Inanother embodiment, switching system 95 a further comprises a secondswitch closable by control system 101 to provide power from the energystorage component 94 to power converter 96, configured to apply anappropriate voltage and/or current to the first and second electrodes.

Switches of the switching system 95 a may be operable via a userinterface 102, via control system 101 or a combination thereof, to openand/or close the one or more switches in a selected sequence and/or at aselected time interval. The selected sequence and/or time intervals maybe determined based on one or more of user input, sensor feedback, orpredetermined values, or a combination thereof. Control system (“controlunit”) 101 may comprise control electronics, and an input receive and beconfigured to implement logic such as ladder logic, or the equivalent,to perform such tasks. For example, control system 101 may be configuredto close a switch upon detecting operation of a push-button of the userinterface 102 by a user, and configured to open the switch upon expiryof a timer, the timer set to expire after a period of time from switchclosing corresponding to the time required to transition the opticalfilter from a dark state to a light state. The period of time may bepredetermined, or based on sensor feedback from monitoring the VLT ofthe optical device to which the control system is coupled. Controlsystem 101 may be configured to select whether to draw power from powersource 92 or energy storage component 94, depending on available powerin each component and/or power needs of the optical device.

User interface 102 is operatively coupled to the control system 101, andmay comprise one or more push-buttons, membrane switches, dials, or thelike, for providing input to the control system 101, which in turnoperates the switching system. In some embodiments, the user interface102 comprises outputs such as annunciators, meters, or screens, forexample to provide an indication to a user of available energy from thepower source 92 and/or energy storage component 94, status of thedevice, or the like. The user interface 102 may be operatively coupledto the control system by signal wires or wirelessly. For an electricalsystem configured to operate on input from one or more sensors, the oneor more sensors provide input for operation of the switching system. Insome embodiments, the electrical system may be configured to switchablybypass the energy storage component, for example by providing analternate electrical path which couples the power source to the opticalfilter and/or other components directly without the energy storagecomponent in series. In some embodiments, the power source and theenergy storage component may concurrently deliver power. For example,the alternate electrical path may be engaged automatically whensufficient power is available from the power source, or it may beengaged manually by operation of a switch or other user input.

Devices and Configurations

In some embodiments, an EHPS and one or more components of theelectrical system may be formed or positioned on a flexible substratematerial. This provides a flexible film which can be laminated onto orbetween transparent window portions, such as sheets of float glass,using an adhesive that provides an optically clear bond (e.g. anoptically clear adhesive such as 8172PCL, available from 3M). In oneembodiment, the transparent window portion is clear or tinted floatglass (for example, as available from PPG Industries of Pittsburgh,Pa.), tempered glass, safety glass or the like. Other materials such aspolycarbonate and other transparent polymer materials can also be usedfor transparent window portions.

Windows or lens systems may be planar or non-planar. A lens of a lenssystem, or a pane, or panes of a window system may be transparent orsubstantially transparent; lenses or panes may have a VLT of about 100%.A flexible film in accordance with the invention may be attached to aplanar or non-planar transparent substrate with adhesive (e.g. anoptically clear adhesive layer such as 8172 PCL from 3M, PVB, EVA orTPU). In one embodiment, the present invention is incorporated into thewindow system by laminating a flexible variable transmittance opticalfilter to a transparent substrate. In another embodiment, a variabletransmittance optical filter is incorporated into a window system bylaminating the flexible variable transmittance optical device filmbetween two transparent panes (e.g. forming a variable transmittancelayer between two rigid panes, such as exemplified in FIGS. 9 and 10).For a non-planar substrate, a flexible VTO filter that is a film may beapplied to the non-planar substrate with tensioning or stretching,and/or the application of heat, to conform the flexible VTO film to thecurve of the non-planar substrate.

Windows comprising a variable transmittance optical filter (“variabletint windows”, “variable transmittance windows”, “smart windows”) may beused in vehicles (e.g. bus, car, train, plane, boat, ferry or the like)or buildings to improve occupant comfort (reduce glare, mediatebrightness, reduce solar heat gain), reduce heating or cooling needs forthe building or vehicle, and/or provide privacy for occupants. Variabletint windows of embodiments of the present invention can be manufactured(e.g. produced at the factory) comprising a variable transmittanceoptical filter, and EHPS, and optionally other components of theelectrical system, or components useful for mounting the window in thebuilding or vehicle (e.g. frame, mounting brackets, hinges or the like).In some embodiments, the variable transmittance optical filter and EHPSmay be installed on an existing window of a building or vehicle (e.g.‘after market’, ‘retro-fitting’). In some embodiments, an insert windowcomprising a variable transmittance optical filter and EHPS may beinstalled for a building with existing windows (‘secondary glazing’,‘storm window’, insert window or the like). For after-marketinstallation, a variable transmittance optical film with EHPS may beapplied to the vehicle window using a suitable adhesive. Control unitsand/or other components of an electrical system for operation of the VTOfilter may be mounted on or nearby the window. Optionally, wirelesscontrols may be used to, for example, initiate application of a voltageto the VTO filter.

Referring to FIGS. 5A and 5B, a schematic diagram of a variabletransmittance window according to various embodiments of the inventionis shown at 103. The window comprises a pane 105, and a VTO filter 106a. Light 104 from a light source is incident on pane 105 and VTO filter106 a, VTO filter 106 a is switched a dark state due to the presence ofUV light in the incident light. The dark state of VTO filter 106 areflects and/or absorbs a portion of the incident light 104, allowingonly a portion 107 of the incident light to be transmitted through thewindow. FIG. 5B shows the VTO filter 106 b after a voltage has beenapplied, rendering the VTO filter to a light state. The light state ofthe VTO filter 106 b allows for a greater portion 108 of the incidentlight to be transmitted through the window. Thus a single window maydemonstrate variable transmittance of light—the portion of incidentlight transmitted is dependent on the particular configuration of theVTO filter, as exemplified herein.

In other embodiments, the window may comprise additional coatings orlayers to block or reflect light in the UV, IR, VIS or NIR range, or acombination thereof. In some embodiments, the adhesive used to apply theVTO film to the window may block a portion of the UV light; or aUV-blocking film may be applied to the window. In some embodiments, thewindow may comprise more than one pane, and a surface of one or morepanes may comprise a low-emissivity (“low-E”) coating or a solar controlcoating. Low-E coatings may be used in building windows to furtherimprove the insulating and/or solar heat gain properties of the window.Emissivity is expressed as a unitless value (emissivity number) andrefers to the heat emitting property of a surface. Perfect emissivityhas a value of 1; untreated window glass has an emissivity of about 0.8to about 0.85; glass with a low-E coating demonstrates reducedemissivity, generally in the range of 0.05 to 0.45. A low-e coating maybe provided on a pane of glass before assembly of the window, or appliedto a pane of the window after assembly. A hard (or pyrolytic) lowemissivity coating may comprise a single layer of a substantiallytransparent, electrically conductive oxide such as an oxide of Sn, Zn,In, W or Mo, or a combination thereof. The low-E coating comprises afurther dopant, such as F, Cl, Sn Al, Ta, Nb, In, Ga or the like—e.g.fluorine-doped tin oxide or tin-doped indium oxide. The coating mayfurther comprise a silicon or silicon oxynitride under layer. Solarcontrol, or heat-reflective, coatings may comprise layers of Ag or Snoxide, and reduce the amount of heat absorbed through the coated glass.Metallic heat reflective coatings may also be electrically conductive.Additional UV, IR, VIS and/or NIR reflecting or blocking may be providedby components of the optical filter, for example some materials used inthe conductive layer may contribute to IR reflection.

Solar heat gain (quantified by a solar heat gain coefficient, or SHGC)is an indicator of the portion of the energy in the solar radiationspectrum that enters the building through the windows as heat. An SHGCof 1 means that all of the energy present in the solar radiationincident on the window enters the building, and a SHGC of 0 means thatnone of the energy in the solar radiation incident on the window entersthe building. A low SHGC may be desirable in a hot climate where airconditioning is used to cool the inside of buildings. In such cases, awindow with a lower SHGC can reduce the amount of energy used for airconditioning. Alternatively a high SHGC can be desirable in morenortherly or southerly climates on cooler days when passive heat gain isdesired. A window with an SHGC that can be varied according to thecondition can be desirable for both reducing air conditioning use on hotdays and for allowing for some passive heat gain on colder days.

In embodiments where the EHPS is a photovoltaic EHPS (PV-EHPS), and theVTO device is a window or an opthalmic device, the PV-EHPS may belocated on, or embedded in the substrate or switching material of theoptical filter, or affixed to a pane of the window, affixed adjacent tothe window, affixed on a frame of the window or the like. In someembodiments, the PV-EHPS may be affixed so as to be exposed to interiorlight of the building, and the device may be powered at least in part byinterior lighting, instead, or in addition to, solar energy. In someembodiments, this may allow for an electrical system without an energystorage component, as interior light may be used to meet the power needsof the self-powered window, for example, in periods of low daylight, orat night. In another embodiment, the electrical system comprises aPV-EHPS disposed for exposure to internal light, and an energy storagecomponent that may be charged by the PV-EHPS, operatively coupled to aself-powered window. Such a configuration may allow for operation of aself-powered window where a light source is the internal light of thebuilding, and the light source is insufficiently energetic for operationof the window and/or electrical system—the PV-EHPS receives theavailable light and charges the energy storage component. When thewindow is to be electrically faded, the power needed for fading may besupplied by the energy storage component.

Where the PV-EHPS is located so as to cover a portion of the visiblearea of the window, the size of the EHPS may be selected to minimizeobscuring the window, while still harvesting a suitable amount of powerfor charging the energy storage component (if present), and/or providinga suitable voltage to effect fading or darkening of the and/or operatethe electrical system of the device. A photovoltaic power source oflimited area, or another power source of limited capacity, can still beused to power the optical device by use of an energy storage device,since the energy storage device can be substantially continuouslycharged, for example by trickle charging, to accumulate energy, whichmay then be used to power the optical device intermittently, since theoptical device may not require a constant large power draw, but may onlyrequire power when switching from dark to light state. In someembodiments, a photovoltaic EHPS may have an area of less than about25%, or less than about 10%, or less than about 5% of one pane of thewindow, or of a first substrate and/or second substrates; in otherembodiments, the photovoltaic power source may have an area from about1% to about 25%, or from about 1% to about 10%, or from about 1% toabout 5%, or any amount or range therebetween. While the efficiency of aPV-EHPS may vary, it is known that the relationship between power outputand size (area) of the PV-EHPS is substantially linear—a larger deviceproduces more power. However, the relationship between the powerrequirement of a hybrid P/E device and the size of the device may not belinear, and thus a smaller than would be expected PV-EHPS may besuitable for providing sufficient power to a hybrid P/E device asdescribed herein. The overall low power draw of a hybrid P/E variabletransmittance optical device may be met by an EHPS small enough to beportable, and in some cases worn by a user (e.g. for providing power toan opthalmic device). Where the device is a window, the PV-EHPS may beincorporated along an edge, in a corner or another less obtrusiveportion of the window itself, without affecting the window. Theefficiency of EHPS, including PV-EHPS, varies widely. A readilyavailable PV-EHPS may be capable of producing about 40 W/m² (about 3.9W/ft²)—one skilled in the art will be aware of PV-EHPS with greaterpower production capabilities.

Self-powered windows according to various embodiments of the presentinvention may exhibit low power requirements for switching. FIG. 14Billustrates the power required (W/m²) relative to device size. As can beseen, the power requirement per unit area (m²) decreases with increasingsize of the variable transmittance optical filter in the device. In someembodiments of the invention the power requirement per unit area (W/m²)relative to device size in meters squared (m²) may be from about 0.0001W/m² to about 25 W/m², or from about 0.001 W/m² to about 10 W/m², orfrom about 0.0005 W/m² to about 5 W/m², or from about 0.001 W/m² toabout 2 W/m², or from about 0.004 W/m² to about 1 W/m², or any amount orrange therebetween. In some embodiments the power requirements, therange of power per unit area of variable transmittance optical filter isfrom about 0.034 W/m² to about 8 W/m² device/optical filter area.

In other examples, the lens of an opthalmic device comprising a hybridP/E switching material and having a surface area of about 0.1 m² toabout 0.2 m² can be faded with about 0.005 to about 0.01 W. For anexemplary automotive window (e.g. a sunroof, side window, rear window orwindshield) having a surface area of about 0.2 m² to about 0.5 m², about0.01 to about 0.02 W of power may be used to fade the lens of theautomotive window. For an exemplary architectural window of about 0.5 m²to about 2 m², about 0.02 to about 0.25 W of power may be used to fadethe lens of the architectural window. For a PV-EHPS capable of producingabout 40 W/m², the area of a photovoltaic array for such applicationswould be about 1.25 to about 3.75 cm² for the opthalmic device; about2.5 to about 5 cm² for the exemplified automotive window; or about5-6.25 cm² for the exemplified architectural window. The powerrequirements may be higher or lower depending on the switching materialused, the construction of the device, the efficiency of the electronics,environmental conditions and/or usage patterns of the device.

Architectural Windows:

For ease of description, a naming convention for reference to theparticular surfaces of the multiple glass panes in an insulating glassunit (IGU), relative to the installation site, is used in the art;surface #1 is the exterior surface of the exterior pane of the windowand consecutive surfaces of consecutive panes are numbered accordingly.A double-pane IGU, for example, would comprise surfaces #1, #2, #3 and#4, according to conventional numbering. Architectural windows may alsobe insert windows (retro-fitted windows, storm windows, secondaryglazings or the like), suitable for installation in an existingbuilding. Insert windows may themselves be an IGU, or may be a singlepane of glass, or an optical filter with two rigid substrates, theinsert window comprising a VTO filter as described herein. In oneembodiment, there is provided an IGU comprising a variable transmittanceoptical filter laminated to surface #1, surface #2, surface#3 or and/orsurface #4 of the panes of the IGU. In a further embodiment, the VTOfilter may be laminated between two panes, and form one pane of the IGU.In another embodiment, the VTO filter may be suspended in the sealed gapbetween two panes. Referring to FIG. 6, a partial cross section of awindow comprising a variable transmittance optical filter (a variabletransmittance window) according to one embodiment is shown generally at110. The illustrated window is an IGU comprising first pane 112 andsecond pane 114. An optical filter 116 is laminated onto surface #1 offirst pane 112 of the IGU and is not in contact with sealed gap 118. Thevariable transmittance optical filter may comprise flexible first andsecond substrates, and may be a film. Spacer 120 provides a seal to formsealed gap 118 along with first and second panes, and the window ismounted in frame 122. Other components of an IGU are omitted for ease ofillustration and clarity, but will be understood by one skilled in theart to be present. Wires 124 connect the optical filter 116 to aconnector 126 that facilitates connection to an electrical systemcomprising an EHPS and other components for operation, such as thoseexemplified herein.

Referring to FIG. 7, a partial cross section of an insulating glass unit(IGU) according to another embodiment is shown generally at 130. IGU 130comprises first pane 112 and second pane 114. A variable transmittanceoptical filter 13 is suspended between first pane 112 and second pane114. Perimeter spacer and seal 132 creates a sealed space 135 betweenfirst pane 112 and optical filter 131. Perimeter spacer and seal 134creates a sealed space 133 between second pane 114 and optical filter131. The embodiment shown in FIG. 7 has two separate sealed spaces 133and 135 on either side of optical filter 131, rather than just onesealed space as with most double-paned IGUs. Insulating glass unit 130can be mounted in frame 122. Wires or electrical connectors 124, 126 areconnected to electrodes in contact with the switching material, and toother components of an electrical system and an energy-harvesting powersource (not shown). Other components of an IGU are omitted for ease ofillustration and clarity, but will be understood by one skilled in theart to be present.

Referring to FIG. 8, a partial cross-section of a variable transmittancewindow according to another embodiment is shown generally at 140. Theillustrated window is an IGU comprising first pane 112, second pane 114,spacer 120, sealed gap 118 and variable transmittance optical filter 116disposed (e.g. laminated) on surface #2 of the first pane. In theembodiment illustrated, an energy-harvesting power source 141, isaffixed to surface #4 of the second pane 114 and operatively coupled toone or more components of the electrical system and the optical filtervia connectors 142 and 143. The window is mounted in frame 144. Othercomponents of an IGU are omitted for ease of illustration and clarity,but will be understood by one skilled in the art to be present. Otherlocations for energy-harvesting power sources may include, oralternately be 141 a—surface #3 of second pane 114, 141 b—the surface ofthe optical filter 116 disposed on surface #2 of the first pane 112, 141c—surface #1 of the first pane 112, 141 d—on an exterior portion offrame 144 and/or 141 e—an interior portion of frame 144. Selection ofthe location of an EHPS may be dependent upon the type of the EHPS, theconfiguration of the window and/or frame, the relative location of theoptical filter; where the EHPS is a PV-EHPS, the PV-EHPS may be locatedso as to receive sufficient exposure to incident light of a suitablewavelength, whether natural or artificial. With consideration of theteachings herein, one skilled in the art will be able to select asuitable location for a PV-EHPS.

Referring to FIG. 9, a partial cross-section of a variable transmittancewindow according to another embodiment is shown generally at 150. Theillustrated window is an IGU comprising a frame 144, first pane 112,second pane 114, variable transmittance optical filter 116 between thefirst pane 112, and a third pane 151. Spacer 120 separates the secondpane 114 from the third pane 151, describing gap 118. Other componentsof an IGU are omitted for ease of illustration and clarity, but will beunderstood by one skilled in the art to be present. Examples of suitablematerials for interlayers in this and other embodiments include PVB(poly-vinyl-butaryl), EVA (ethyl-vinyl-acetate), TPU (thermoplasticpolyurethane), pressure sensitive adhesives (PSA) or the like. Inembodiments illustrated in FIG. 9 and FIG. 10, the variabletransmittance layer may comprise a cutaway region to accommodate EHPS153 between panes 112, 151. In an alternate embodiment, panes 112, 151may be substrates, each comprising a conductive layer and accommodate aswitching material therebetween—the panes and switching materialtogether comprise an optical filter, with connectors configured to applya voltage to the switching material. Wires 152 connect the EPHS tocontrol system components 145 comprising push-button 146. Otherconnectors (not shown) provide electrical connection between the EPHS,the variable transmittance layer and other components as may beappropriate. The control system 145 comprises control electronics; inother embodiments, components of the electrical system may be locatedelsewhere. Operation of the push-button 146 operates a switch in thecontrol electronics, causing appropriate voltage and/or current to beapplied to the electrodes of the optical filter, effecting fading of theoptical filter. In some embodiments, operation of the switch may alsoinitiate a timer, to limit the amount of time the voltage and/or currentis applied to the optical filter.

Referring to FIG. 10, a perspective sectional view of a self-poweredvariable transmittance window is shown generally at 160. The illustratedwindow is an IGU comprising a frame 144, first pane 112, second pane114, variable transmittance optical filter 116 between second pane 114and third pane 151. Spacers 120, gap 118 are indicated; other componentsof an IGU are omitted for ease of illustration and clarity, but will beunderstood by one skilled in the art to be present. In some embodiments,variable transmittance optical filter 116 may be laminated between firstpane 112 and third pane 151 with optically clear interlayers. The devicefurther comprises an energy-harvesting power source 161. In theillustrated embodiment the PV-EHPS is affixed to a portion of a surfaceof the IGU. An electrical system for electrically connecting theelectrodes of the variable transmittance layer with the EHPS andcontrols may comprise connectors 162 (between the EHPS and controls) andconnectors 163 between the controls and electrodes of the variabletransmittance optical filter 116. Routing of conductors is forillustrative purposes only, other configurations may be preferred ornecessitated by design of the window, frame and/or installation site ofthe window. Control system 145 is mounted on a portion of frame 144,however it will be apparent to those skilled in the art that otherlocations are possible. Control system 145 comprises a push button 146which may be activated by a user to initiate a transition of theswitching material from a dark state to a light state. In otherembodiments, control system 145 may be replaced or supplemented withdistributed components; in other embodiments, the control may furthercomprise automated control components, sensors, additional usercontrols, displays or the like.

As will be apparent to those skilled in the art, upon consideration ofthe teachings herein, an EHPS may alternately, or additionally, bedisposed on any of surfaces #1, #2, #3, or #4 or additional surfaces ofan IGU having more than two panes, and/or the frame of the window. Infurther embodiments (not illustrated), the EHPS may be configured forattachment to a wall or surface adjacent to the window, and connected tothe electrical system, the optical filter and other components of theelectrical system by connectors.

Gaps 118, 133 and/or 135 may be filled with a gas such as air, argon,krypton, nitrogen or other gas, or may be evacuated (e.g. vacuuminsulated glass, evacuated glazing), as is known to be used in an IGU.

There is further provide methods of making a variable transmittance IGU.In one embodiment, a method of making a variable transmittance IGUcomprises the steps of: a) providing a first pane having a variabletransmittance optical filter laminated thereto; b) providing a secondpane; c) attaching the first pane to the second pane via a perimeterseal, thereby defining a sealed space between the first and the secondpane; and optionally d) establishing a vacuum within the space orfilling the sealed space with a gas. The first pane may be attached tothe second pane placing the VTO filter in contact with the sealed space.In another embodiment, the first pane may be attached to the second paneplacing the VTO filter not in contact with the sealed space. Optionally,the step a) may further comprise a step of laminating a pane (a thirdpane) to the VTO filter, forming a sandwich structure. The method mayfurther comprise a step of mounting the attached first and second panesin a frame, the frame configured to facilitate installation of thevariable transmittance window into a building. Optionally, for any orall of steps a) and b), the first and/or second pane may comprise acoating. Optionally, any or all of steps a) and b) may further comprisea step of applying a coating to a surface of a pane, examples of suchcoatings include anti-glare coatings, anti-reflective coatings,IR-reflective coatings, low-e coatings, UV blocking films or UV blockingcoatings.

In another embodiment, there is provided an insert window comprising avariable transmittance optical filter. Where the insert window is asingle-pane insert window (e.g. not an IGU), a VTO filter may belaminated to surface A (e.g. the surface of the pane facing the exteriorof the building when the insert is installed) and/or surface B (e.g. thesurface of the pane facing the interior of the building when the insertwindow is installed) of the panes of the insert window. Where the insertwindow is itself an IGU, the VTO filter may be laminated to surface #1,#2, #3, or #4 of the insert, as described supra. In a furtherembodiment, the VTO filter may be laminated between two panes withsuitable interlayers (forming a variable transmittance layer), and thisvariable transmittance layer comprise a pane of the insert window. Inanother embodiment, the VTO filter, or variable transmittance layer maybe suspended in the sealed gap between two panes of an IGU.

Referring to FIG. 15, a schematic cross-sectional diagram of variabletransmittance insert window according to some embodiments of theinvention is shown generally at 351. The walls 352 of a building definea window opening. A single pane window 353 is located in a windowopening defined by walls 352 of a building, and held in place by frame353 a. As single pane windows generally have poor insulative or solarheat gain rejection properties, their presence may require aconsiderable expenditure of energy to heat the building, or keep itcool. An insert window comprising a single pane 355 is installed in thewindow opening, interior to the single pane window 353. The insertwindow further comprises a variable transmittance optical filter 357 inthe form of a film laminated to surface A of the insert window (e.g.facing the exterior of the building), and a low-emissivity (low-E)coating 356 on surface B of the inset window (e.g. facing the interiorof the building). Embodiments where the low-E coating is on surface A ofthe insert window, and the variable transmittance optical filter is onsurface B of the insert window, or where the low-E coating and thevariable transmittance optical filter are both on surface A or surface Bare also contemplated, and may be constructed and operated according tomethods described herein. Original single pane window 353 and insertwindow 355 have a gap 351 a therebetween. In the embodiment shown, thegap may or may not be a sealed gap, but can provide an insulating layerof air between the windows. The illustrated insert window furthercomprises a power source 358 and control system 359 that form part of anelectrical system. The electrical system receives power from the powersource 358 for application to the window (in an automated manner, and/orin response to an input received by the control system), and foroperation of other components of the electrical system, as describedherein. Operation of the variable transmittance insert window isdescribed herein. In some embodiments, the power source is an energyharvesting power source, such as a photovoltaic power source. In someembodiments, the variable transmittance window may be electricallyconnected to the building's power system, to provide power to operatethe window. The insert window is mounted in frame 354, and the framedinsert window is in turn slidably mounted in track 354 a. The lowerportion of frame 354 is seated in the bottom portion of track 354 a,while there is a gap 352 a between the upper portion of frame 354 andthe upper portion of track 354 a. Track 354 a is configured to allow aclose fit with frame 354 while allowing lateral sliding of the insertwindow, and vertical movement of the insert window to facilitate removalof the framed insert window if desired. Gap 352 a accommodates manualremoval of the framed insert window to by lifting upward and angling outthe bottom portion of the framed insert window. Alternatively, frame 354could be attached directly to the window opening defined by the buildingwalls 352. The variable transmittance optical filter (for thisembodiment it may be a film) 357 can be attached to glass 355 using apressure sensitive adhesive (PSA) or the like.

A low-E coating increases the energy efficiency of the insert window byreducing the heat absorbed by the glass 355 from the inside of thebuilding and by reducing the emission of heat from the glass 355 to thebuilding when the glass 355 is hotter than the inside of the building.Hard coat low-E coatings, typically applied using a pyrolytic processare known in the art to be more durable than soft-coat low-E coatingsand more tolerant of contact or abrasion. An example of a glass 355 witha hard-coat low-E coating that can be used is Sungate 500 made by PPG.

Referring to FIG. 16, a schematic cross-sectional diagram of an insertwindow according to another embodiment is shown generally at 361. Walls352 of a building define a window opening. A single pane window 353 islocated in a window opening defined by walls 352 of a building, and heldin place by frame 353 a. A double-pane insert window is installed in thewindow opening. In some embodiments the double-pane window is an IGU.The IGU comprises a first pane 369 and a second pane 366, the first andsecond panes separated along their periphery by spacer 387, and sealedby seal 388. A gap 367 a may be filled with air or another gas, or maybe a vacuum. The IGU of the illustrated embodiment further comprises avariable transmittance optical filter 368 in the form of a film appliedto surface #2 of the first pane, and a low-E coating 367 on surface #3of the second pane of the IGU. The variable transmittance optical film368 can be applied using a pressure sensitive adhesive. The IGU ismounted in frame 370, attached to building walls 362. Original singlepane window 353 and the insert window 355 describe a gap 351 atherebetween. The illustrated insert window may further comprise a powersource and control system, and an electrical system (not shown). Theelectrical system receives power from the power source for applicationto the window (in an automated manner, and/or in response to an inputreceived by the control system), and for operation of other componentsof the electrical system, as described herein. Operation of the variabletransmittance insert window is described herein. In some embodiments,the power source is an energy harvesting power source, such as aphotovoltaic power source. In some embodiments, the variabletransmittance window may be electrically connected to the building'spower system, to provide power to operate the window.

In alternative embodiments, variable transmittance film 368 can beapplied to surface #1, #3, or #4, and low-E coating 367 can be appliedto surfaces #1, #2, or #4. In some embodiments, variable transmittanceoptical filter may be applied to a pane, and a low-E coatingsubsequently applied to the variable transmittance optical filter. Thepane so prepared may subsequently be used in a window, insert window orIGU as described herein.

An advantage of applying the variable transmittance optical film 368 tosurface #2 is that any heat absorbed by the variable transmittanceoptical film 368 (particularly in its dark state) is separated from theinside of the building by insulating air gap 367 a of the IGU insertwindow. The low-E coating can be a soft-coat or a hard-coat low-Ecoating. In some embodiments, a low-E coated glass (e.g. Solarban glassavailable from PPG) may be used for the second pane 366.

Referring to FIG. 17 a schematic cross section of an insert window isshown generally at 371. The ‘single pane’ insert window formed fromlaminated glass comprises a variable transmittance optical film 374laminated between a first pane 376 and a second pane 373 withinterlayers 375 between the film and panes 376, 373. Surface A of theinsert window (facing the exterior of the building when installed has alow-E coating 377 applied thereto. In alternate embodiments, the low-Ecoating may be applied to an interior-facing surface of the insertwindow. The insert window is mounted in frame 354, and the framed insertwindow may be mounted in a track 354 a as described.

Referring to FIG. 18 an insert window according to another embodiment ofthe window is shown generally at 381 comprising a variable transmittanceoptical filter 384 laminated between a first pane 383 and a second pane385 with interlayers 375 as described, and then formed into an IGU byadding a third pane 366 separated from the laminated structure byspacers 387 and sealant 388. The IGU can be mounted into a frame 370 inorder to facilitate installation into an existing window frame on theinterior side of an existing window. The IGU structure providesexcellent insulating properties. If combined with an existingsingle-pane window, the insulating value (known as the U-value) of theentire window can approach that of triple-glazed windows. In thisexample, a low-E coating 367 is applied to surface #3 of the IGU. Inother embodiments, the low-E coating can be applied on any of thesurfaces #1, #2 or #4. Selection of the surface for the low-E coatingmay depend on the building type and/or geographical location.

Insert windows with variable transmittance optical filters can be usedto increase the energy efficiency of a building without replacing theexisting glazing. In some cases, as glazings are a part of the buildingenvelope, replacement of existing glazing may not be possible, orpractical due to cost, aesthetic reasons and/or regulations—a variabletransmittance insert window may overcome one or more of these obstacles,for example, when retrofitting a building for energy efficiency.

In some embodiments, windows according to various embodiments may havethe EHPS positioned so that it is exposed to the interior lighting ofthe building, for example. The EHPS may thus be powered all or in partby the interior lighting.

A myriad of fastening, framing and mounting systems for installation ofarchitectural windows are known in the art, selection of a particularsystem or method may be dependent on the particulars of the window andthe site of installation, such as the configuration of the windowopening in the building envelope, construction materials, nature of thewindow, local building codes or the like. Examples of window fastening,framing and/or mounting systems include those described in US2011//0063061, describing a magnetic attachment system; US 2011/0078963describing a press-fit storm window system comprising flexible gasketsfor a friction fit of the insert window in the existing window frame; US2011/0047875 describing a storm window frame comprising clips to lockthe frame in place and bulb seals to provide a seal; U.S. Pat. No.3,837,118 describes a hung window sash system wherein the sashes areinstalled in a flush track in a window jamb; U.S. Pat. No. 5,806,256describes a modular glazing system that may be used for removablemounting of insert windows; U.S. Pat. No. 5,649,389 describes aninterior storm window assembly for mounting to an interior building wallover a window opening; U.S. Pat. No. 4,370,830 describe a frame forslidable mounting of a window in a wall of a building; U.S. Pat. No.6,256,931 describes a window retention system comprising a frame andslidable window mounting for use with the window retention system. It iswithin the ability of one skilled in the art to select a fastening,framing or mounting system suitable for the installation site and/orspecific design of window.

Vehicle Windows:

Windows comprising a variable transmittance optical filter (“variabletint windows”, “variable transmittance windows”) may be used in vehicles(e.g. bus, car, train, plane, boat, ferry or the like) to improveoccupant comfort (e.g. reduce glare, mediate brightness, provideprivacy, reduce solar heat gain or the like).

In some embodiments, the invention further provides for a self-poweredvariable transmittance window of a vehicle, and methods of making suchwindows. The window may be a sunroof, rear, front and/or side window ofa vehicle, and may comprise a variable transmittance layer, an energyharvesting power source and electrical system components for operationof the window. The windows may further comprise a frame or gasket and/orother components for installation of the device.

Two or more variable transmittance windows in a vehicle may have thesame, or different VLT in light and dark states, and/or same ordifferent contrast ratios. For example, a vehicle may have a sunroofwith about 10% VLT in a dark state and about 30% in a light state (˜3:1contrast ratio), while a side or rear window may have about 15% VLT in adark state and about 60% VLT in a light state (˜4:1 contrast ratio).Greater VLT and/or a higher contrast ratio may provide increasedvisibility. This may be desirable to provide vehicle passengers with abetter view outside. Solar heat gain through rear or side windows may begenerally less than would occur with a sunroof. For front (windshield)and side-front windows where driver visibility is of greater importance,a variable transmittance window with greater VLT than is used in therest of the vehicle's windows may be selected. In one embodiment, frontside window has a visible light transmittance of 20% in the dark stateand 80% in the light state. In some embodiments, a portion of the windowof the vehicle may comprise a portion that has variable transmittance.For example a top portion of a front window may comprise a variabletransmittance optical filter that darkens with exposure to sunlight, andmay be cleared automatically with application of a voltage when a lightsensor indicates reduced light outside, or in response to a driverspreference by activation of a switch to initiate application of avoltage. For a vehicle with multiple variable transmittance windows,each window may be independently controlled, or the multiple windows maybe simultaneously controlled as a group via a control system.

The substrate for a variable transmittance window for a vehicle (e.g.“automotive window”) may be tempered automotive glass, polycarbonate,acrylic or the like. A variable transmittance window for a vehicle maycomprise first and second substrates and a variable transmittanceoptical filter as illustrated generally in FIG. 1, the variabletransmittance optical filter comprising a switching material asdescribed herein. The variable transmittance window may further comprisea power source, such as an energy harvesting power source, and anelectrical system configured to receive power from the power source andto provide a voltage to a first electrode and a second electrode of thevariable transmittance optical filter. The variable transmittance windowmay further comprise a frame, such as a generally C-shaped gasketsurrounding the periphery of the window. Electrical system and powersources, including energy harvesting power sources as described hereinmay be used in the variable transmittance window. A variabletransmittance optical filter may be laminated to one side of the windowusing an adhesive, such as 8172 PCL, as described herein. Alternately, avariable transmittance optical filter may be laminated between twosubstrates with interlayers, as described above.

The variable transmittance window may automatically darken when exposedto light comprising wavelengths of about 350 to about 420 nm (e.g. forembodiment where the switching material is a hybrid P/E switchingmaterial). Activation of a switch (e.g. by control electronics or by auser) applies power from the power source to the first and secondelectrodes of the variable transmittance window and fades the window.

Opthalmic Devices:

The invention further provides for a self-powered variable transmittanceophthalmic device, and methods of making such a device. Variabletransmittance ophthalmic devices are configured to darken when exposedto a light source, and lighten when a voltage is applied to the opticalfilter of the device. Opthalmic devices according to various embodimentsof the invention comprise an energy-harvesting power source, and a lens,the lens comprising an optical filter as described herein. The lens maybe a prescription lens. Where the optical filter is a film, the film maybe applied to the lens. Examples of opthalmic devices includesunglasses, glasses, sports eyewear such as goggles or cycling glasses,safety eyewear, visors, shields or the like; prescription or otherwisethat may be used to aid or protect a user's vision, mediate brightness,reduce glare, reduce eyestrain, and/or protect a users' eyes from UV orIR light. In some embodiments a variable transmittance opthalmic devicemay further comprise a UV and/or an IR blocking component, layer orfilm. The UV and/or IR blocking component may be located on the ‘inside’of the lens (e.g. the surface closest to a user's eye, or between thelight source and the user's eye) to block UV light reaching a user's eyewithout interfering with the UV light induced photochromism of thevariable transmittance optical filter; alternately, the UV blockingcomponent may be located on the ‘outside’ of the lens (surface farthestaway from the user's eye) to reduce or block the UV light reaching auser's eye, and also block the amount of UV light available to inducephotochromism of the variable transmittance optical filter. For a lenshaving a curved surface, the concave surface may be the ‘inside’; UV/IRblocking components may be on the concave surface. The variabletransmittance optical filter may be on the inside or outside of thelens. An energy harvesting power source may be incorporated into theophthalmic device, for example as part of a lens, attached to the frameor other component of the optical device, or operatively coupled to theophthalmic device by a wire and worn on a piece of clothing, forexample.

Referring to FIG. 11, an opthalmic device according to one embodiment ofthe invention is shown generally at 170. The device comprises variabletransmittance lenses 171 positioned in front of the eyes, with frame 172and arms 173. Incorporated into the frame are an EHPS 174 and a button176 for activation by a user. Control unit 175 on the opposite side ofan EHPS and switch comprises additional components of the electricalsystem for operation of the device. In the embodiment shown, the EHPS ison the outside of each of the arms 173, with the control unit on theinside of the arms 173. The lens darkens automatically when exposed tolight, when a light state is desired by a user, button 176 is actuatedby the user and a voltage is applied to the lens 171, and the lensswitches from a dark state to a light state, allowing for an increase inVLT. Frame 172 may be made of any suitable material, for example metalor plastic, or a combination thereof. The lens may be made of anysuitable transparent material, for example, glass or polymer; examplesof polymers include plastics, acrylic, polycarbonate or the like.

The optical filter of the invention can be incorporated into ophthalmicdevices in a variety of ways. In one embodiment, the optical filteritself is made into the variable transmittance lens. In anotherembodiment, the optical filter is attached to the lens of an ophthalmicdevice.

Operation

To control the operation of the variable transmittance optical filter ofembodiments of the present invention, the filter is controllably coupledto a power source by a control circuit of the electrical system asdescribed herein. The coupling facilitates establishing a suitablepotential difference (voltage) between the electrodes of the opticalfilter and providing a sufficient current to the electrodes forestablishing a desired electric field therebetween. A single variabletransmittance window can be connected to one control circuit, ormultiple variable transmittance windows can be connected to a singlecontrol circuit. Control electronics (control circuits, or controlcircuitry) incorporated into the electrical system allow harvesting,storage and/or use of the harvested power to be controlled. Control maybe automated, semi-automated, or manual (user-controlled). A controlsystem may further include electronic circuitry to apply an alternatingwaveform to the VTO filter of the device, instead of a constant DCvoltage.

Control electronics can also include electronic circuitry to apply apulsed or alternating waveform to the optical filter instead of aconstant DC voltage. The waveform can be in the form of a square wave, asawtooth wave, a sinusoidal wave, or some other waveform. The amplitudeof the wave can vary. In one embodiment, a square wave can be applied tothe electrodes of the optical filter by control electronics. The squarewave can range from amplitude of about −2 Volts to about +2 Volts. Whenone of the electrodes is at 2 Volts, the other transparent electrode isat 0 Volts. In one embodiment, the waveform varies from 0 to a positivevoltage at one electrode and the other electrode varies from 0 to acorresponding negative voltage. In another embodiment, the waveformvaries from about 0 to about 2 Volts at one electrode and from about 0to about −2 Volts at the other electrode. Applying the voltage to theelectrodes as a square wave may reduce the lightening time and/orincrease the cycle life of the optical filter. In one embodiment, thefrequency of the waveform is 100 Hz. In a further embodiment of theinvention, waveform frequencies range between about 0.1 Hz to about1,000 Hz. In another embodiment, waveform frequencies range betweenabout 0.001 Hz to about 100 KHz.

A voltage converter, timer and/or a voltage regulator may also beincluded. Timer circuits may be implemented by relays or other digitalor analog circuitry, as understood in the art. FIG. 12 graphicallyillustrates the response of a hybrid P/E optical filter to anapplication of voltage at the electrodes operatively coupled thereto Theline 180 illustrates the % VLT exhibited by the optical filter of thedevice over time; line 181 represents the voltage difference betweenfirst and second electrodes. Before time a 312, the optical filter is ina dark state (˜15% VLT for this embodiment), and there is substantiallyno voltage difference at the electrodes. At time a 182, a voltage isapplied to the electrodes, providing a voltage therebetween (˜2 V forthis embodiment), and the electrochromic fading of the switchingmaterial proceed, reducing the % VLT over time interval a-b, reaching afaded state (˜65% for this embodiment) at time b 183. The voltageapplied to the electrodes is reduced to substantially zero after thefaded state is reached at a time after time b, or about time c 184. Inthe absence of further stimulus (UV light), the device remains in thefaded state. Thus, to transition the optical filter to a light state,the electrodes need to be driven between time a 182 and at least time b183, but may not require constantly applied voltage at other times tomaintain the light state.

User-control of a variable transmittance device (window, lens or thelike, such as exemplified herein) may be effected by a user-activatedswitch or function, via a button, touchpad or the like, such as thoseexemplified herein. When exposed to UV light (e.g. natural sunlight, orsome interior light sources), the device achieves a dark state. Totransition to a faded state, the switch (e.g. a “CLEAR” switch or“CLEAR” function) is activated and a voltage is applied to the devicefor a predetermined period of time. The period of time may be controlledby a timer, and determined empirically based on incident light, deviceconstruction and/or formulation (e.g. faster or slower switching time,presence or absence of UV blocking films, thickness of the switchingmaterial or the like), and may be from about 10 seconds to about 5minutes, or any amount or range therebetween. When the predeterminedamount of time has elapsed, the switch is reversed and voltageapplication to the device stopped. If the device is no longer exposed toUV light, it will remain in the faded state. If the device is exposed toUV light, the photochromic darkening reaction will occur and the windowwill return to the dark state, until or unless additional voltage isapplied to the device.

In some embodiments, the optical filter will begin to darken again whenexposed to UV light, thus may transition from light to dark over time inabsence of applied voltage. If it is desired that the device bemaintained in a faded state, while subject to UV from incident light,voltage may be applied to the device over a prolonged period of time. Insome embodiments, a second switch or function (e.g. a “HOLD” switch or a“HOLD” function) may be provided for user operation in this manner.Activation of the switch or function causes a voltage to be appliedcontinuously to the device until the application is stopped, e.g. by asecond pressing of the switch or cancelling of the HOLD function.

The optical filter may be maintained at an intermediate VLT state orrange (e.g. between first and second intermediate % VLTs, the firstintermediate % VLT less than the % VLT of the fully dark state, and thesecond intermediate % VLT is greater than the % VLT of the fully fadedstate, and less than the first intermediate % VLT) by application ofvoltage during the auto-darkening of the variable transmittance opticalfilter (in response to incident light). The first and secondintermediate % VLT may be predetermined (e.g. programmed into a controlsystem), or may be set by a user, for example by a potentiostat ormulti-position switch. Alternately, an intermediate state may beachieved by interrupting or disconnecting the electric voltage duringthe fading process. For example, a user may control the VLT bycontrolling the electric field applied to the filter. The intermittentapplication of voltage may be initiated and terminated by a user (e.g.by operation of a switch); alternately, application of voltage may befully or partially automated, and the application of voltage initiatedand/or terminated by control electronics of the system. The voltage maybe applied to a filter intermittently that is in the process ofdarkening.

Additionally, the control electronics may comprise an LED or otherindicator light(s) to indicate the status of voltage application to thedevice (off or on). Other control schemes can be used to provide inputfor the power control electronics, and different types and numbers ofswitches and buttons can also be used. In a further embodiment, the oneor more buttons are replaced with a three position knob.

Preparation of Self-Powered Variable Transmittance Optical Devices.

The present invention provides, in part, methods of preparingself-powered variable transmittance optical devices, and methods ofpreparing films for use in such devices.

A method for preparing a self-powered variable transmittance deviceaccording to some embodiments of the invention comprises the steps of a)providing a first transparent substrate, b) disposing a layer ofswitching material on the substrate, c) providing an energy harvestingpower source and d) providing an electrical system for coupling theenergy-harvesting power source to the switching material. The method mayfurther comprise, following any one of steps b), c) or d) a step ofapplying to the layer of switching material a second substrate, therebyforming a ‘sandwich’ of a layer of switching material between first andsecond substrates.

In another embodiment of the invention, a method for preparing aself-powered variable transmittance device according to some embodimentsof the invention comprises the steps of a) providing a first transparentsubstrate with a conductive layer disposed thereon, b) disposing a layerof switching material on the conductive layer of the substrate, c)providing an energy harvesting power source and d) providing anelectrical system for coupling the energy-harvesting power source to theswitching material. The method may further comprise, following any oneof steps b), c) or d) a step of applying to the layer of switchingmaterial a second substrate with a conductive layer disposed thereon,thereby forming a ‘sandwich’ of a layer of switching material betweenconductive layers of the first and second substrates. In someembodiments, the first conductive layer may be applied and/or etched soas to provide two or more electrically separated electrodes.

Variable transmittance optical filters used in devices may be preparedaccording to methods known in the art. For example, roll-to-rollprocessing methods may be used for making a variable transmittanceoptical filter. Roll-to-roll methods may be particularly suited to thepreparation of flexible variable transmittance optical filters in theform of films. Such methods generally comprise the steps of a) providinga first flexible substantially transparent substrate comprising a firstconductive layer (a first electrode), b) disposing a layer of switchingmaterial on the conductive layer of the first substrate, c) providing asecond, flexible substantially transparent substrate comprising a secondconductive layer (a second electrode) and laminating the secondsubstrate to the switching material, the switching material contactingthe first and second electrodes over substantially all of the area ofthe switching material, d) providing an energy harvesting power sourceand an electrical system comprising connectors for connection of theenergy harvesting power source to the first and second electrodes.

The method may further comprise after step d), a step of applying theoptical filter to a lens of an optical device, or a pane of a window.The method may further comprise after step d) a step of affixing theenergy harvesting power source to a substrate of the optical filter. Thestep of applying the optical filter to a lens or pane may compriseapplication of an adhesive (e.g. PSA, PVB, EVA, TPU or the like) to thelens or pane, and/or the optical filter.

Methods in accordance with some aspects of the invention generallycomprise disposing a layer of switching material on a firstsubstantially transparent substrate, and optionally between the firstsubstrate and a second substantially transparent substrate, theswitching material capable of transitioning between a light state and adark state based at least in part on application of an electric voltage.For example, the switching material may be capable of transitioning froma light state to a dark state on exposure to UV radiation and from adark state to a light state with application of an electric voltage. Afirst and second electrode may be provided such that the switchingmaterial is substantially in contact with the first and secondelectrodes. In some embodiments, the electrodes are disposed on thesurface of at least one of the substrates. In some embodiments, theelectrodes may be disposed on a surface of the switching materialitself. The methods further comprise providing an energy harvestingpower source. In some aspects the power source is a photovoltaic EHPSThe methods further comprise providing an electrical system configuredto receive power from the energy harvesting power source and to providepower to the first electrode and the second electrode for application ofthe electric voltage through the first and second electrodes, therebyelectrically connecting the first electrode and the second electrode tothe energy harvesting power source.

A method in accordance with other aspects of the present inventioncomprise disposing a layer of switching material on a firstsubstantially transparent and flexible substrate and optionally betweenthe first substrate a second substantially transparent and flexiblesubstrate. The switching material capable of transitioning between alight state and a dark state based at least in part on application of anelectric voltage. For example, the switching material may be capable oftransitioning from a light state to a dark state on exposure to UVradiation and from a dark state to a light state with application of anelectric voltage. A first electrode and a second electrode are flexiblydisposed on the surface of at least one of the substrates such that theswitching material is proximate with the first and second electrodes.The method further comprises disposing a flexible energy-harvestingpower source on the device film, such as a photovoltaic energyharvesting other power source. The method further comprises disposing aflexible electrical system on the device film. The electrical system isconfigured to receive power from the energy-harvesting power source andto provide power to the first electrode and the second electrode forapplication of the electric voltage through the first and secondelectrodes, thereby electrically connecting the first electrode and thesecond electrode to the energy-harvesting power source. In someembodiments, the electrical system may comprise an energy storagecomponent, such as a battery, capacitor or super capacitor, or array ofbatteries, capacitors or super capacitors, disposed on the device film.The energy storage component may be flexible, inflexible, or it may bean array of flexibly interconnected but substantially smallsub-components. The method may comprise forming each component of aflexible self-powered variable transmittance optical device film on oneor more layers of thin, flexible material. Multiple such layers may thenbe laminated together to form the completed optical device film.

In accordance with another embodiment of the invention, there isprovided a method of making a variable transmittance window pane, themethod comprising: providing a transparent window pane, applying avariable transmittance optical filter to a surface of the pane,providing a power source electrically connected to the electrodes of thevariable transmittance optical filter, and providing an electricalsystem configured to receive power from the power source and to providea voltage to the electrodes of the variable transmittance opticalfilter.

In accordance with another embodiment of the invention, there isprovided a method of making a variable transmittance window pane, themethod comprising providing first and second transparent panes andlaminating a variable transmittance optical filter between the first andsecond panes with interlayers, providing a power source electricallyconnected to the electrodes of the variable transmittance opticalfilter, and providing an electrical system configured to receive powerfrom the power source and to provide a voltage to the electrodes of thevariable transmittance optical filter.

The variable transmittance window pane may be an architectural windowsuch as an insert window, or may be used as a first or second pane in anIGU. The variable transmittance window pane may be a vehicle window,such as a sunroof, windshield, rear or side windows of a car.

The vehicle window may be installed in a vehicle during production (e.g.as part of the processes of an assembly line), or may be installedafter-market. Therefore, embodiments of the invention further providefor a vehicle comprising a device according to various embodiments ofthe invention; in some embodiments, the device is a vehicle window.

The architectural window may be installed in a building duringconstruction, or may be installed after-market (e.g. retrofitting).Therefore, embodiments of the invention further provide for a buildingcomprising a device according to various embodiments of the invention,in some embodiments the device is an architectural window.

The variable transmittance window pane may comprise part of an IGU. Thevariable transmittance pane may be assembled into an IGU duringmanufacture (e.g. on a production line of a glazing factory), or may beinstalled after the IGU is assembled. Therefore, embodiments of theinvention further provide for an IGU comprising a device according tovarious embodiments of the invention; in some embodiments, the device isa variable transmittance window pane.

In some embodiments, the variable transmittance insert window may beinstalled after construction (retrofitting), by a consumer. The variabletransmittance insert window according to various embodiments of theinvention may comprise a portion of a kit, along with instructions forits installation and/or operation. Therefore, embodiments of theinvention further provide for a kit comprising a variable transmittanceinsert window. The kit may further comprise mounting hardware, framinghardware, attachment hardware or the like to aid in installation of theinsert window. Various types of hardware for such purposes will be knownin the art.

The variable transmittance optical filters described in the followingexamples have been prepared with hybrid photochromic/electrochromicswitching materials and have been included to demonstrate generalproperties of the hybrid photochromic/electrochromic switching materialsin the format of an optical filter. It will be understood that thefollowing examples are intended to illustrate some embodiments of theinvention and are not intended to limit the invention in any way.

Example 1 Preparation of Selected Hybrid P/E Compounds

S001 and S002 were Prepared as Described in U.S. Pat. No. 7,777,055.

Synthesis of S042

Synthesis of 3-bromo-2,5-bis(4-(tert-butyl)phenyl)thiophene: (30)

Sodium carbonate monohydrate (58.0 g, 468 mmol) was dissolved in water(500 mL) and a solution of 4-(tert-butyl)-phenylboronic acid (40.0 g)and 2,3,5-tribromothiophene (30.0 g, 94 mmol) in THF (500 mL) was added,and deoxygenated by bubbling with argon. Pd(PPh₃)₄ (5.0 g, 4.30 mmol)was added and the mixture refluxed for 24 h. The mixture was cooled andthe aqueous phase separated and extracted with EtOAc. Organic fractionswere combined washed with water (500 mL) and dried over MgSO₄. Thesolvent was evaporated and the crude product washed in MeOH, filteredand dried overnight to afford a light yellow, powdery solid (35.46 g,89%).

Synthesis of S042(3,3′-(perfluorocyclopent-1-ene-1,2-diyl)bis(2,5-bis(4-(tert-butyl)phenyl)thiophene)

A solution of (30) in anhydrous THF/ether cooled to −45° C. and treatedwith nBu—Li-(2.5 M in hexanes, 35 mL, 87 mmol) dropwise under a n argonatmosphere. The reaction mixture was stirred for a further 15 minutesfollowed by addition of octafluorocyclopentene (5.6 mL, 41.5 mmol) usinga cooled gas tight syringe. The reaction was allowed to stir until thetemperature reached −10° C., quenched by the addition of 10% HCl (50mL). The aqueous layer was separated and extracted with ether. Theorganic phases were separated and pooled, dried over MgSO₄, filtered andsolvent removed by rotary evaporation. The crude product was stirred inMeOH for 3 hours, and the resulting precipitate filtered, dried andpurified using flash chromatography (hexanes), affording 2 fractions—F1was pure S006 (TLC), F2 contained S006 along with a fluorescentbyproduct by TLC. F1, 5.35 g, 14.8%) and F2, 10.4 g (˜75% pure, 22%) aslight yellow, powdery solids. ¹H NMR (400 MHz, CDCl₃) δ 7.37 (d, J=8.5Hz, 4H), 7.30 (d, J=8.5 Hz, 4H), 7.05 (d, J=8.4 Hz, 4H), 6.92 (d, J=8.4Hz, 4H), 6.13 (s, 2H), 1.34 (s, 18H), 0.91 (s, 18H).

Synthesis of S0543,3′-(perfluorocyclopent-1-ene-1,2-diyl)bis(2,5-bis(4-methoxyphenyl)thiophene)

Synthesis of 3-bromo-2,5-bis(4-methoxyphenyl)thiophene (37)

2,3,5-Tribromothiophene (6.42 g, 20 mmol), 4-methoxyphenylboronic acid(6.38 g, 42 mmol) and sodium carbonate (8.5 g, 80 mmol) were stirred inTHF/water mixture (125/50 ml) for 90 min at RT under argon flushing.Pd(PPh₃)₄ (693 mg, 0.6 mmol) was added. The mixture was refluxed for 16h (TLC), cooled to RT and THF was removed by evaporation. Water wasadded and aqueous fractions extracted with EtOAc. The organic fractionswere combined, solvent removed and the crude product purified by flashchromatography (Silica gel; hexane/chloroform/EtOAc; gradient up to 20%chloroform then 20% EtOAc) to yield3-bromo-2,5-bis(4-methoxyphenyl)thiophene (4.9 g, 13 mmol, 65%).

Synthesis of S054: Compound (37)

(10.64 g; 28.4 mmol) was dissolved in anhydrous ether (350 mL) andcooled to −25° C. n-BuLi (14.2 mL; 35.5 mmol; 2.5 M in hexane) wasadded. The mixture was stirred at this temperature for 0.5 h.Octafluorocyclopentene (1.9 mL; 14.2 mmol) was added in two portions,and the reaction was allowed to warm slowly over 3 h. The reaction wasquenched by addition of 10% aqueous HCl (50 mL). Organic layer wasseparated and the aqueous was extracted with EtOAc (250 mL). Solventfrom the combined organic extracts was evaporated and crude material waspurified by column chromatography (Silica gel; hexanes/EtOAc up to 30%).Collected product was sonicated in methanol and pale yellow powder wasfiltered and dried in air (4.46 g; 5.82 mmol; yield 41%). ¹H NMR (400MHz, CDCl₃) δ 7.32 (d, J=8.7 Hz, 4H), 6.91 (dd, J=8.7, 2.4 Hz, 9H), 6.60(d, J=8.6 Hz, 4H), 6.25 (s, 2H), 3.85 (s, 6H), 3.41 (s, 6H).

Synthesis ofS068—12,12′-((4,4′-(perfluorocyclopent-1-ene-1,2-diyl)bis(5-(4-(tert-butyl)phenyl)thiophene-4,2-diyl))bis(4,1-phenylene))bis(12-methyl-2,5,8,11-tetraoxatridecane)

Synthesis of 2-(2-(2-methoxyethoxy)ethoxy)ethyl 4-methylbenzenesulfonate (46)

To a solution of p-toluenesulfonyl chloride (3.17 g, 19.3 mmol) in 20 mLof pyridine was added 2-(2-(2-methoxyethoxy)ethoxy)ethanol (4 g, 21mmol), stirred at 0° C. for 12 h and at RT for 2 h. To this suspension,water and hexanes and ethyl acetate were added and separated. Theorganic layer was neutralized with dilute HCl and separated again;organic fractions were pooled, dried (MgSO₄ and NaHCO₃), filtered, andconcentrated under reduced pressure to give 4.87 g, 15.3 mmol (79%) of2-(2-(2-methoxyethoxy)ethoxy)-ethyl 4-methylbenzene sulfonate as acolorless oil.

Synthesis of S068

Sodium hydride (0.24 g, 6 mmol, 60% dispersion in oil) was washed withhexanes (6 mL) and a solution of di-alcohol S067 (1.33 g, 1.52 mmol) inTHF (25 mL) was added under argon. The reaction mixture was stirred for1 h at RT. To the resulting suspension was added a solution of (46)(1.06 g, 3.35 mmol) in anhydrous dimethylformamide (12 mL) in oneportion and the mixture was stirred for 48 h. The reaction was quenchedby addition of brine (100 mL) and extracted with EtOAc (3×100 mL). Theorganics were combined, washed with water (2×100 mL), dried over MgSO₄,filtered and evaporated to dryness. The residue was purified by columnchromatography (Silica gel; hexane/EtOAc (50/50) as the eluent to obtain1.24 g (1.06 mmol; 70%). ¹H NMR (400 MHz, CDCl₃) δ 7.44 (d, J=8.4 Hz,4H), 7.36 (d, J=8.4 Hz, 4H), 7.09 (d, J=8.4 Hz, 4H), 6.96 (d, J=8.3 Hz,4H), 6.21 (s, 2H), 3.72-3.68 (m, 12H), 3.66 (t, J=5.3 Hz, 5H), 3.61-3.57(m, 4H), 3.43-3.37 (m, 10H), 1.58 (s, 12H), 0.95 (s, 18H).

Example 2 Preparation of Variable Transmittance Optical Filters

Method A:

An ITO-coated PET substrate having a thickness of 7 mil (˜178 microns)and a sheet resistance of 50 ohms/square (OC50, made by CP Films) is cutinto two 15 cm×15 cm sheets. The substrate may be cleaned before use,and is temporarily laminated to glass plates to facilitate handling.Steel spacers are positioned at the perimeter of the PET, to set the gapfor the final pressed device (from 20-70 microns). A volume of switchingmaterial (below, heated to facilitate dispensing), is placed on the PETto completely fill the gap between the PET sheets when the device ispressed. A second piece of glass-backed PET is placed on top, so thatthe PET sheets overlap such that there is some ITO coating exposed, toact as the external electrical contacts. The sandwich(glass-PET-switching material-PET-glass) is placed in the center of apress platens (heated to 45° C.). Pressure greater than 160 psi isapplied to the filter using a Carver hydraulic press, or nip rollers,for a time sufficient to allow the switching material to attain auniform thickness (at least 10 seconds, up to about a minute, or up toseveral hours). After the pressure is released, the glass plates areseparated, any excess switching material is wiped off and conductivetape is applied to the exposed ITO. Total thickness of an optical filter(e.g. ITO-coated PET+switching material) is about 16 mil (˜406 microns),including a 2 mil (˜51 microns) layer of switching material.

Method B:

An ITO-coated PET substrate is prepared as described above. A switchingmaterial comprising a low-boiling solvent (e.g. THF as per Formulation#7) is then coated onto the conductive side of a first sheet ofITO-coated PET using a slot die, a knife coater, or other roll-to-rollcoating method (according to manufacturer's instructions). The thicknessof the coater is set such that the final coating once the low-boilingsolvent is evaporated off is the desired thickness. For example, toobtain a final switching material thickness of about 50 microns, theinitial wet coating may be set to about 114 microns. The low-boilingsolvent is evaporated from the switching material using blown air orheat or a combination of both. A second layer of ITO-coated PET islaminated on top of the coating with the conductive side in contact withthe switching material to form a sandwich structure. The laminatedstructure is cut to the desired size (if required) and electricalcontacts (e.g. busbars) added. An exemplary optical filter produced inthis manner demonstrated a total thickness of about 16 mil (˜406microns), with a switching material layer of about 2 mil (˜51 microns).

Example 3 Preparation of the Switching Material

The switching material was formulated to demonstrate how the componentsof the formulation can be varied. These formulations can be readilyadapted to a desired application by a worker skilled in the art, byreplacing the listed ingredients with one or more other ingredients inaccordance with embodiments of the present invention. Table 1 sets outformulations for switching material that may be used in a deviceaccording to various embodiments of the invention. Compounds that may beused in the formulations include those according to Formulae IA/IB, andthose illustrated herein. In some examples, the compound used in aformulation may be S001, or a derivative thereof having a functionalgroups on one or more of the four peripheral thiophene rings; or S002,or a derivative thereof having a functional group on one or more of theperipheral phenyl rings; or S042, or a derivative thereof having anotherfunctional group on one or more of the peripheral phenyl rings; or S054,or a derivative thereof having another functional group on one or moreof the peripheral phenyl rings; or S068, or a derivative thereof havinga functional group on one or more of the peripheral phenyl rings.

PEGDMA, solvents, electrolytes, initiators, charge carriers,co-solvents, polymers and other formulation components are availablefrom commercial suppliers (e.g. Sigma-Aldrich); or as indicated.DAROCUR™ is available from CIBA Specialty Chemicals of BaselSwitzerland, a division of BASF. PVB B-90 is available from Butvar, adivision of Solutia Inc. of St. Louis, Mo.

Formulation #2 was prepared for photostationary state (PSS)determination, using 2×10⁻⁵ M of the indicated compound, in a solvent(triglyme).

TABLE 1 Switching Material Formulations Type of Formulation formulationFormulation (% wt of components) component component 1 3 4 5 6 7 8 9hybrid P/E 3 3 5 3.4 3.4 2 0.5 5 compound solvent triglyme 75 74 72 70.770.6 28.8 93.5 cyclopentanone 89 tetraglyme GBL electrolyte LiClO4 1 1 1TBAPF6 1 1 1 0.4 1 polymer PEGDMA860 15 PMMA 15 5 5 PVB B90 22 24.9 258.8 initiator DAROCUR 0.01 charge carrier TBPA 6 6 HALS A cosolvent THF60 charge DNB 1 compensator PB Total (wt %) 100 100 100 100 100 100 100100

Formulation #7, upon removal of co-solvent (evaporation) yields aswitching material according to Formulation #4.

Hybrid P/E compounds used in formulation #1 include S001 or a derivativethereof having different functional groups on the four peripheralthiophene rings, or S002 or a derivative thereof having differentfunctional groups on the four benzene rings. Hybrid P/E compounds usedin formulation #2 include S054 or a derivative thereof having differentfunctional groups on the four benzene rings. Hybrid P/E compounds usedin formulation #3 include S001 or a derivative thereof having differentfunctional groups on the four peripheral thiophene rings, or S002 orS042 or a derivative thereof having different functional groups on thefour benzene rings. Hybrid P/E compounds used in formulation #4 includeS001 or a derivative thereof having different functional groups on thefour peripheral thiophene rings, or S054 or a derivative thereof havingdifferent functional groups on the four benzene rings. Hybrid P/Ecompounds used in formulation #5 include S054 or a derivative thereofhaving different functional groups on the four benzene rings. Hybrid P/Ecompounds used in formulation #6 include S001 or a derivative thereofhaving different functional groups on the four peripheral thiophenerings, or S054 or a derivative thereof having different functionalgroups on the four benzene rings. Hybrid P/E compounds used informulation #7 include S054 or a derivative thereof having differentfunctional groups on the four benzene rings. Hybrid P/E compounds usedin formulation #8 include S042. Hybrid PIE compounds used in formulation#9 include S001.

Example 4 Optical Properties of Switching Material

The optical properties of the switching material are tested with samplesof the switching material. The VLT spectrum of formulation #3 comprisingS001, S002 or S042 were determined for light and dark states. An OceanOptics spectrometer was used to measure the % visible lighttransmittance of the sample, in its light and dark states, over anelectromagnetic spectrum. The formulation is first exposed to UV lightto switch to the dark state, decreasing the transmittance of thematerial in the visible range between about 400 and about 750 nm. Anelectric charge of 2 Volts is then applied to the switching materialsample for 3 minutes, causing the sample to revert to its light state.In the light state, more light is permitted to pass through theswitching material resulting in an increase in percent transmittance inthe range from 400 to 750 nm. An exemplary spectra for S001 demonstrateda VLT in the light state of about 80%, and the visible lighttransmittance in the dark state is about 20%. This provides a contrastratio of 4.

The sensitivity of the switching material to the intensity of UV lightwas also studied. Formulation #2 was exposed to both UV light at 365 nmand solar radiation (using a solar simulator) with and without a UVblocking film made by Energy Film of Portland, Oreg. The Energy Film UVblocking film acts as a band-pass filter and effectively blocks the highintensity UV light (below about 365 nm). As illustrated in FIG. 13,depicting the absorbance spectra of the switching material under thevarious UV light intensities, the switching material maintainssensitivity to the low intensities of UV light (above about 365 nm) todarken. FIG. 13 shows a plot of the absorbance spectra of S054 intriglyme in a faded state (solid line); darkened using a 365 nm lightsource without (open circle) or with (open square) EnergyFilm™; anddarkened using a solar simulator without (solid circle) or with (solidsquare) EnergyFilm™. In a faded state (solid line), the absorbance ofthe formulation is reduced to baseline. Absorbance reaches a maximum atabout 620-240 nm for all sample treatments, with the maximum absorbancevarying with light source and presence or absence of a partial UVblocking layer. Highest absorbance is reached for a UV light sourcewithout EnergyFilm™—about 0.265. Placement of the UV blocking layerbetween the sample and light source reduces the maximum absorbance toabout 0.254. Simulated full spectrum sunlight provides a maximumabsorbance in the dark state of about 0.105; inclusion of the UVblocking layer reduces the maximum absorbance to about 0.055.

Example 5 Visible Light Transmittance (VLT) Determination of the OpticalFilter

The VLT of the optical filter prepared by method A described in Example2 comprising formulation #4 with S054 was measured using an Ocean Opticsspectrometer. Optical filters exposed to 365 nm UV light for about 3minutes had a VLT of 17%. The transmission increased after applicationof a charge of 2 Volts for about 3 minutes to 69%.

Example 6 Haze Determination of the Optical Filter

The clarity of the optical filter prepared by method A described inExample 2 comprising formulation #4 with S054 or S001 was measured usinga XL-211 Hazegard Hazemeter manufactured by BYK Gardner. The haze of theoptical filter was measured to be about 2%.

Example 7 Switching Speed Determination of the Optical Filter

Switching speed is determined by the amount of time it takes for theoptical filter to go from the dark state to the light state, and viceversa. To transition from the light state to the dark state, the opticalfilter is exposed to 365 nm UV light for 3 minutes. To transition fromthe dark state to the light state, a charge of 2 Volts is applied to thefilter for 3 minutes. Switching time from the light state to the darkstate is measured as the time required to achieve 90% of the VLT of thedark state from the fully light state. Switching time from the darkstate to the light state is measured as the time required to achieve 90%of the VLT of the light state, from the fully dark state.

The optical filter prepared by the method A described in Example 2comprising the switching material that had been prepared according toformulation #4 comprising S001 or S054, the optical filter comprising aUV blocking film (Energy Film) applied to the glass-backed PET oppositeto the switching material, was tested. The switching speed of theoptical filter is about 30 seconds from the light state to the darkstate, and about 2 minutes for switching from the dark state to thelight state. The switching speed of the optical filter preparedaccording to formulation #1 comprising S001 or S002 was measured to beabout 35 seconds from the dark state to the light state and 2 minutesfrom the light state to the dark state. The switching speed of theoptical filter prepared according to formulation #7 with S054, measuredto be about 3 minutes 20 seconds from the dark state to the light stateand 12 seconds from the light state to the dark state. The switchingtime for transitioning from the light state to the dark state can bedifferent from the switching time for transitioning from the dark stateto the light state.

Example 8 Photostability Determination of the Optical Filter

Photostability of the optical filter is determined by exposing thesamples to UV light similar to the UV light in the solar spectrum.Samples are tested at regular intervals to determine degradation. Whenthe contrast ratio has dropped to 50% of the original contrast ratio ofthe device (determined prior to testing), the device is considered tohave failed. The photostability of the optical filters is determinedusing a QUV accelerated weathering tester from Q-Labs. Photostability ofthe optical filter is also determined using an S16 accelerated testinginstrument from Solar Light to test the photostability of the opticalfilter at higher power densities. The photostability of the opticalfilter made according to the method described in Example 2 comprisingformulation #5 using S054 was tested on a QUV for 1300 hours at about7.3 mW/cm² before 50% degradation was reached. The same optical filterwas tested on a Solar Light unit at 135 mW/cm² for 540 hours before 50%degradation was reached.

Example 9 Cycling Durability Determination of the Optical Filter

Cycling durability is determined by exposing the optical filter tocontinuous UV light using a Spectroline transilluminator and applying avoltage to the optical filter at regular time intervals. First, theamount of time required to darken and lighten the optical filter isdetermined. This is then used to determine how much time the voltageshould be turned on and off for in the automated test. Typically, thevoltage “on” time is set to be the amount of time it takes for theoptical filter to bleach to about 90% of its initial value. The voltage“off” time is set to be the amount of time it takes for the opticalfilter to darken to 90% of its original value. The cycling is thencontrolled by an automated cycling set-up using a PC, a LabJackinstrument (available from LabJack Corporation of Lakewood Colo.). Inthe “off” state, the two electrodes are shorted together to dissipatethe charge on the optical filter.

The cycling durability of an optical filter made according to the methoddescribed in Example 2 comprising formulation #6 comprising S054, with aUV blocking film (Energy Film) applied to the glass-backed PET oppositeto the switching material, was tested. To observe the effect of ambientatmosphere on the durability of the device, a first preparation of theformulation (6-1) was prepared at the bench (exposed to ambientatmosphere), and a second preparation of the formulation (6-2) wasprepared in an oxygen-free atmosphere (glove box). The optical filtercomprising formulation 6-1 demonstrated 741 switching cycles beforereaching a 50% degradation point (the contrast ratio decreased to 50% ofthe starting contrast ratio). In comparison, the optical filtercomprising formulation 6-2 demonstrated 1553 cycles before reaching a50% degradation point.

Example 10 Sheet Resistance Determination of the Optical Filter

The operability of optical filters using substrates of different sheetresistances was tested. Optical filters were made according to themethod described in Example 2 comprising formulation #4 with S001 orS054 and ITO-coated substrates of 50 Ohms/square, 100 Ohms/square, and300 Ohms/square. Optical filters were also made comprising formulation#8 with S042, and ITO-coated substrates of 1,000 Ohms/square, and100,000 Ohms/square. The optical filters were tested for the ability totransition between light and dark states. In all examples the opticalfilters were still able to lighten upon application of electricity;optical filters with lower sheet resistance s were observed to switchfaster.

Example 11 Required Voltage Determination of the Optical Filter

To determine the minimal voltage required to cause the optical filtersto switch from the dark state to the light state, incrementally highervoltages are applied until the device begins to transition from the darkto the light state. In an optical filter made according to the methoddescribed in Example 2 comprising the switching material that had beenprepared according to formulation #4 with 5001 or S054, fading from thedark to light state is observed at about 1.8 Volts. The transitioning isfaster at about 2 Volts. It has been observed that too high a voltagemay not be desirable because other electrochemical reactions may beintroduced that may cause fouling of the electrodes. For example,transitioning in the optical filter is impacted when a voltage greaterthan about 2.5 volts is applied, and brown spots are observed if theoptical filters are left at that potential for a longer period of time.

Example 12 Intermediate States of the Optical Filter

A prototype device made using formulation #3 comprising S001, S002 orS042 was tested for the ability to achieve intermediate states. Thedevice was first darkened under UV light (365 nm) although solar lightcan equally be used. A DC voltage of about 2 Volts was then applied tothe device for a short period of time (e.g., about 10% of the totalswitching time) before being switched off. During the time the power wasapplied the VLT of the device increased, but did not go all the way tothe light state. Once the voltage was switched off, the device remainedin its intermediate dark state without the need for any furtherapplication of power. If the voltage is turned on again, the devicecontinued to transition to its light state.

Example 13 Photostability of Chromophores in Switching Materials of theOptical Filter

The photostability of chromophores in various combinations of theswitching material, are tested by exposing the combination to UV lightsimilar to the UV light in the solar spectrum. Optical filterscomprising the combination are tested at regular intervals to determinedegradation. When the contrast ratio of a device drops to 50% of theoriginal contrast ratio (determined prior to testing), the device isconsidered to have failed. The photostability of an optical filtercomprising the combination is determined using a QUV or QSUN acceleratedweathering tester from Q-Labs, or an S16 accelerated testing instrumentfrom Solar Light (SL) to test the photostability of the combination athigher power densities. Chromophores were tested in combination withvarious switching material components prepared according to Example 2and the results are shown in Table 2 below. Each chromophore was capableof achieving 700 hours in at least one of the combinations of switchingmaterial before 50% degradation was reached.

TABLE 2 Formulation and flexible devices tested. All devices employedEnergyFilm ™ UV blocker applied externally, save for Device #26. Device25 included an additional acetate layer. All devices employed OC50substrate, save for Device #32 (glass substrate) and Device #2 (graphenesubstrate). PB - 50 nm layer of Prussian blue electrochemicallydeposited on electrodes. Device Formulation Thickness Chromophore avgint Failure No. Size (cm) (μ) (%) Polymer (%) Solvent Electrolyte (%)Additives method (mW/cm²) (hours) 1 1.5 (ø) 60 S001 (3) PVB (25)Triglyme SL 120 438 2 1.5 (ø) 60 S001 (3) PVB (25) Triglyme SL 130 288 31.5 (ø) 50 S001 (3) PVB (25) Triglyme SL 110 255 4 1.5 (ø) 60 S068 (3)PVB (25) Triglyme SL 110 191 5 9 × 6 50 S054 (3.5 PVB (25) Triglyme QUV9.8 1537 6 2.5 × 2.5 50 S0689 20) PVB (25) Triglyme QUV 9.8 1130 7 9 × 650 S054 (3) PVB (25) Tetraglyme TBAPF6 (1) QUV 9.8 1073 8 2.5 × 2.5 50S068 (15) PVB (25) Triglyme QUV 9.8 1037 9 1.5 (ø) 50 S054 (3.5) PVB(20.2) Triglyme TBAPF6 (1) HALS A SL 95 104 10 2.5 × 2.5 50 S068 (10)PVB (25) Triglyme QUV 9.8 901 11 1.5 (ø) 60 S001 (3) PVB (25) TriglymeQUV 9.8 865 12 1.5 (ø) 50 S054 (3.5) PVB (20.2) Triglyme TBAPF6 (1) SL110 76 13 3 × 5 50 S054 (3) PVB (25) Triglyme PB QUV 9.8 837 14 9 × 6 50S054 (3) PMMA (25) Triglyme QUV 9.8 801 15 9 × 6 50 S054 (3) PEMA (25)Triglyme QUV 9.8 794 16 9 × 6 50 S054 (3) PVB (25) Triglyme QUV 9.8 78717 1.5 (ø) 60 S068 (3) PVB (25) Triglyme QUV 9.8 772 18 9 × 6 50 S054(3) PVB (25) Tetraglyme QUV 9.8 636 19 9 × 6 50 S054 (2) PVB (24)Triglyme TBAPF6 (1) QUV 9.8 608 20 9 × 6 50 S054 (3.5) PEMA (25)Tetraglyme TBAPF6 (1) QUV 9.8 586 21 2.5 × 2.5 50 S068 (5) PVB (25)Triglyme QUV 9.8 572 22 9 × 6 50 S054 (3) PMMA (25) Tetraglyme QUV 9.8543 23 3 × 5 50 S0549 3.5) PVB (25) Tetraglyme TBAPF6 (1) PB QUV 9.8 52224 3 × 5 50 S054 (3.5) PVB (25) Tetraglyme TBAPF6 (1) QUV 9.8 522 25 3 ×5 50 S054 (6) PVB (22) Triglyme TBAPF6 (1) Qsun 5.6 688 26 7.5 × 7.5 50S054 (5) PVB (25) Triglyme QUV 9.8 386 27 9 × 6 36 S054 (1.5 PVB (24)Triglyme TBAPF6 (1) QUV 9.8 358 28 9 × 6 25 S054 (2) PVB (24) TriglymeTBAPF6 (1) QUV 9.8 293 29 2.5 × 2.5 50 S068 (2..5) PVB (25) Triglyme QUV9.8 136 30 9 × 6 50 S054 (1.7) PMMA (25) PC QUV 9.8 64 31 9 × 6 50 S054(3.5) PVB (25) GBL QUV 9.8 21

Example 14 Impact of Optical Filter on Electrical Consumption and CO₂Emissions

The ability of a variable transmittance window of embodiments of thepresent invention to provide significant energy and cost savings wasdetermined. A building with variable transmittance IGUs was modeledusing window and energy modeling software (Window 6, Optics5) availablefrom Lawrence Berkeley National Laboratories of Berkeley, Calif.). Thebuilding modeled was a 400 square foot small office with a 0.9wall-to-window ratio. The building was modeled in five U.S. cities(Miami, Los Angeles, New York, Houston, and Chicago). The variabletransmittance smart window used for the model is an insulating glassunit with an optical filter laminated onto one of the panes, and a lowemissivity coating on the inside of the exterior pane facing the sealedspace. The variable transmittance smart window used for the model was aninsulating glass unit (IGU) with an optical filter laminated onto one ofthe panes, and a low emissivity coating on the inside of the exteriorpane facing the sealed space. A variable transmittance window of thisconfiguration was determined to achieve a solar heat gain coefficient(SHGC) of about 0.15 in the dark state, and about 0.32 in the lightstate. Using this variable transmittance window in the dark stateresulted in average electricity savings of 28%, according to the model.The electricity savings resulted from a reduced requirement for airconditioning due to the variable transmittance windows. CO₂ emissionswere reduced from about 19% to about 25%, due mostly to the reduction inelectricity usage.

The variable transmittance window of the model achieves a solar heatgain coefficient (SHGC) of about 0.15 with a corresponding percentvisible light transmittance (VLT) of about 10% in the dark state. In thelight state, the percent visible light transmittance of the variabletransmittance window increases to about 58-60%, and the solar heat gaincoefficient increases to 0.32. In the dark state, the variabletransmittance window has a significantly lower solar heat gaincoefficient than standard low-emissivity (“Low-E”) glass. Standard Low-Eglass in the same model achieves an SHGC of about 0.36, with a VLT ofabout 60-62%. Standard float glass (no coatings) in the same modelachieves an SHGC of about 0.68, with a VLT of about 68%. Solarban 70XLGlass from PPG Industries (Pittsburgh, Pa.) in the same model achievesan SHGC of about 0.24, with a VLT of about 47%. The standard float glasshas the highest solar heat gain coefficient while Solarban 70XL glasshas the best SHGC of the non-dynamic glazings. The SHGC of an IGU usingstandard float glass is about 0.70 (according to the dataset includedwith the software). The SHGC of an IGU made using the Solarban 70XLglass is about 0.25 (according to the dataset included with thesoftware). The model demonstrates that an SHGC of less than 0.25 can beachieved with variable transmittance smart windows and dynamic glazings.In this example, the modeled variable transmittance window was assumedto have a contrast ratio of about six.

Example 15 Photovoltaic Panel Size

As the size of the optical filter increases, power demand of the devicemay increase, and the relationship of power demand to device size mayaffect selection of the type and/or configuration of an energyharvesting power source. A constant voltage of about 2 volts was appliedto a variety of sizes of optical filters comprising a hybrid P/Eswitching material (windows, lenses and test devices), and current drawanalyzed to determine the steady-state current of the optical filterafter 5 minutes of applied voltage (all devices had achieved a fadedstate by this time). FIG. 14A shows a plot of power draw (W) vs. devicesize (m²) of the devices of Table 3 (with trend line), demonstrating anon-linear relationship between power draw (P=VI) and device size. Table4 sets out examples of power requirements for devices of various sizes,according to some embodiments of the invention.

TABLE 3 Current and power draw for hybrid P/E devices of varying size.Steady Steady Steady State Max State State Power Device Area CurrentCurrent Power per m2 # Size (W × H) (cm2) [mA] [mA] [mW] [W/m2] 1B 7.7cm × 56.98 12.4 0.183 0.341 0.060 7.4 cm 2 7.7 cm × 56.21 10.6 0.3050.609 0.108 7.3 cm 3 7.6 cm × 57 10.5 0.403 0.803 0.141 7.5 cm 4 7.7 cm× 57.75 12.4 0.256 0.511 0.089 7.5 cm 6 24.4 cm × 607.56 32.7 3.1496.282 0.103 24.9 cm 9 4.4 cm × 12.76 2.9 0.049 0.097 0.076 2.9 cm D360280 cm × 6504 62.7 7.9 16.195 0.025 81.3 cm

TABLE 4 Power requirements for switching of variable transmittanceoptical filters comprising a hybrid P/E switching material, for varioussize devices. Device size (m²) Power (W) Example devices 0.001-0.1  0.001-0.008 Opthalmic devices 0.1-1  0.008-0.02 Opthahnic devices,vehicle windows, architectural windows 1-2  0.02-0.025 vehicle windows,architectural windows 2-4 0.025-0.03 vehicle windows, architecturalwindows 4-6  0.03-0.034 vehicle windows, architectural windows  6-100.034-0.04 architectural windows

As illustrated in FIGS. 14A and B, and set out in Tables 3 and 4, thepower requirement of a hybrid P/E device increases with increasing sizeof the device however this relationship is not linear, and the powerdraw per unit area can decrease as the area of the device increases(illustrated in FIG. 14B). The range of wattage per unit area of deviceis from about 0.0034 w/m² to about 8 w/m² of optical filter in a device.This reduced power requirement for devices comprising a hybrid P/Eswitching material may be of particular interest for applications suchas architectural glass involving large areas (windows), as the powerrequirements of the large windows may be satisfied with a relativelysmall power source compared to ‘smart’ windows using other types ofvariable transmittance technologies. For small devices, while thewattage per unit area for a small device appears large (e.g. 8 W/m² forsmallest devices), the device area itself may be small (e.g. lens of anopthalmic device.

While the efficiency of a photovoltaic energy harvesting power sourcemay vary, it is known that the relationship between power output andsize (area) is substantially linear—a larger device produces more power.As an example, a lens of a ski goggle may have an area of about 17×6 cm(about 0.1 m²), and fading of the ski goggle lens would be expected todraw about 0.007-0.008 W. For a solar cell capable of producing at least3.9 W/ft² (41.97 W/m²), about 28 mm² of solar cell area would beexpected to meet this ski goggle lens power draw. An exemplaryautomotive sunroof of about 38×63 cm (about 0.24 m²), would be expectedto draw about 0.01-0.02 W; a solar cell of the same efficiency wouldrequire an area of about 273 mm² would be expected to meet thissunroof's power draw. An exemplary window of about 36×58 inches (91×147cm, or about 1.33 m²) would be expected to draw about 0.019-0.02 W; thesame efficiency solar cell of about 602 mm² would be expected to be ableto meet this window's power draw.

Example 16 Insert Window

Several insert window configurations were modeled for U-value, solarheat gain coefficient (SHGC), and visible light transmittance (VLT)using window modeling software packages Optics5 and Window6.3, availablefrom Lawrence Berkeley National Laboratories of Berkeley, Calif.—URL:http//windows.lbl.gov/materials/optics/). The insert windows weremodeled with a 63.5 mm (2.5″) gap between the insert window and theexisting (single pane, exterior) window. For insert windows that areIGUs, the surfaces of the IGU insert window are numbered as describedherein. For insert windows that are not IGUs, the surfaces of the paneare referred to as surface A and surface B—surface A, when the insertwindow is installed faces the exterior of the building, and surface Bfaces the interior of the building. A glass pane with a low-emissivity(low-E) coating on it used for the configurations is Solarban 70XL; aglass pane with a hard coat low-E coating on it is Sungate 500. Aflexible film variable transmittance optical filter (VTOF) comprisesfirst and second ITO-coated PET substrate films with switching materialdisposed therebetween as described herein; a rigid variabletransmittance optical filter (VTOF) comprises a flexible film opticalfilter laminated between a first pane and a second pane with PVB. Therigid VTOF may be the single pane of the insert window (e.g.configuration C), or may be a pane of an IGU insert window (e.g.configurations E, F and F-2). First, second and optional third panes maybe 3 mm float glass.

Single Pane: a single pane clear glass window with no treatments orcoatings (e.g. as may be found in an older installation; not an IGU).For the model, this is the existing window in the building (e.g. 353 ofFIGS. 15 and 16).

Configuration A: a single pane insert window comprising a low-E hardcoat on surface A and a flexible VTO filter laminated to surface B usinga pressure sensitive adhesive (PSA). Configuration A is a relativelylight insert window, about 17-24 lb for a 15 ft² window.

Configuration B: a single pane insert window comprising a flexible VTOfilter laminated to surface A using a PSA. Configuration B is arelatively light insert window, about 17-24 lb for a 15 ft² window.

Configuration B-2: a single pane insert window comprising a low-Ecoating on surface B and a flexible VTO filter laminated to surface Ausing PSA. Configuration B-2 is a relatively light insert window, about17-24 lb for a 15 ft² window.

Configuration C: an insert window comprising a rigid VTO filter and alow-E hard coat on surface A. Configuration C is a medium weight insertwindow, about 34-48 lb for a 15 ft² window. FIG. 17 illustrates a rigidVTO filter comprising first and second panes, and a flexible VTO filterlaminated therebetween with PVB.

Configuration D: an insert window comprising a rigid VTO filter and alow-E hard coat on surface B. Configuration C is a medium weight insertwindow, about 34-48 lb for a 15 ft² window. FIG. 17 illustrates a rigidVTO filter comprising first and second panes, and a flexible VTO filterlaminated therebetween with PVB.

Configuration E: an IGU insert window as shown in FIG. 16, comprising aflexible VTO filter laminated to surface #2 of the IGU, a low-e coating(soft coat) on surface #3 of the IGU, and a 12.7 mm gap with argon fillConfiguration E is a moderate weight insert window, about 34-48 lb for a15 ft² window.

Configuration F: an IGU insert window as shown in FIG. 18 comprising avariable transmittance layer (comprising PVB interlayers) between thefirst pane (the pane facing the exterior of the building when the insertwindow is installed) and a third pane (first and third panes providesurfaces #1 and #2 of the IGU). Configuration F comprises a low-E softcoat on surface #3 of the IGU and a 12.7 mm gap with argon fill.Configuration F is a heavier weight insert window, about 51-72 lb for a15 ft² window.

Configuration F-2: an IGU insert window similar to configuration F, butwith the low-E coating on the opposite side of the gap (argon gap). Thewindow comprises a variable transmittance layer comprising a variabletransmittance optical filter and PVB interlayers between the first paneand a third pane (first and third panes provide surfaces #1 and #2 ofthe IGU). Configuration F-2 comprises a low-E soft coat on surface #2 ofthe IGU and a 12.7 mm gap with argon fill. Configuration F-2 is aheavier weight insert window, about 51-72 lb for a 15 ft² window. Table5 shows the results of the modeling of the different insert windowconfigurations A-F.

TABLE 5 VLT, SHGC and U-Value of modeled windows of configurations A-F.Window Properties Single Pane A B C D E F F-2 B-2 VLT - Untinted 0.8990.668 0.718 0.69 0.69 0.516 0.532 0.532 0.668 VLT - Tinted N/A 0.2520.273 0.272 0.271 0.197 0.212 0.212 0.252 SHGC - Untinted 0.86 0.6790.701 0.687 0.628 0.323 0.345 0.287 0.613 SHGC - Tinted N/A 0.652 0.6510.649 0.548 0.204 0.231 0.205 0.521 SHGC Change N/A 0.027 0.05 0.0380.08 0.119 0.114 0.082 0.092 U-Value (W/m2-K) 5.912 2.143 2.831 2.082.094 0.981 0.964 0.964 2.156

FIGS. 19A-C provide bar graphs of VLT, SHGC, and U-Value for modeledwindows of configurations A-F. FIG. 19A shows the VLTs of the differentconfigurations modeled. Only a single VLT is shown for the base singlepane case because the window does not have variable transmittance. Forconfigurations A through F, F-2, and B-2, VLTs are shown in the lightstate (bars with hashed lines) and in the dark state (solid bars) foreach configuration. The same variable transmittance optical film wasused in each configuration. The IGU insert windows (configurations E, Fand F-2) demonstrate reduced light transmission overall in both dark andfaded states because these devices comprise at least one additionallayer of glass (relative to configurations A-D), as well as anargon-filled gap. The presence of a low-E coating also serves to reducethe overall VLT of the insert window. Modeled windows provided acontrast ratio of about 2.50 to 2.65. Other ratios may be obtaineddepending on the thickness and/or composition of the switching material(e.g. type and concentration of hybrid P/E compound) as describedherein.

FIG. 19B shows the SHGC values for the insert window configurationsmodeled. The hatched bars represent the SHGC when the insert window isin the light state, and the solid bars represent the SHGC when theinsert window is in the dark state. All of the insert windowconfigurations modeled demonstrated lower SHGC values compared to thesingle pane base case for both the dark and light states. This canprovide increased energy efficiency through reduced air conditioningcosts. The single pane insert windows demonstrate moderate SHGCreductions compared to the original single pane windows. Of thesingle-pane insert window configurations, configuration B-2 demonstratesthe best SHGC reduction. Configuration B-2 comprises a variabletransmittance film facing the exterior of the building and the low-Ecoating oriented facing the interior of the building. This is anunexpected result—low-E coatings are known in the art to be optimallyoriented facing an air gap (e.g. surface #3 of a conventional IGU) inpart to protect the low-E coating from handling or abrasion, however theinteraction and impact off the positioning of a VTO filter and low-Ecoating on SHGC has not been previously investigated. For a single-paneinsert window, this would mean the low-E coating should be orientedfacing the exterior side of the building (surface A, as perconfiguration A, with VTO filter on surface B). However, configurationB-2 (low-E on surface B, with VTO filter on surface A) showssignificantly lower SHGC characteristics than configuration A. This isconsistent with the trend observed for the rigid VTO filter windows ofconfiguration C and D. Configuration D, which has a low-E coating facingthe interior of the building, also demonstrates lower SHGC values thanconfiguration C, which has the low-E coating facing the exterior of thebuilding.

The three IGU configurations (E, F, and F-2) demonstrate the greatestSHGC reductions. IGUs are known to generally provide better thermalinsulation than a single pane, however the interaction and impact of thepositioning of a VTO filter and low-E coating on SHGC in an IGU used asan insert window has not been previously investigated. For theconfigurations tested, the VTO filter is mounted away from the interiorof the building (laminated to surface #2 for configuration E, or betweensurfaces #1 and #2, for configurations F and F-2). The variabletransmittance optical filter can absorb light in its dark state andheats up as a result. If the VTO filter is located next to thebuilding's interior, the heat can be transferred more easily into thebuilding, whereas when the VTO filter is separated from the interior ofthe building by an air gap, and in some configurations, an additionalpane of glass, less heat is transferred into the building (hence thelower SHGC value). Soft-coat low-E coatings may have a greater impact onSHGC values than hard-coat low-E coatings because soft-coat low-Ecoatings can reflect near-infra-red (IR) radiation, further reducing theheat entering the building. An IGU insert window may be desirable forsome installations in that it provides a greater SHGC reduction, howeverthe increased weight and cost of the IGU insert window should also beconsidered.

FIG. 19C shows the U-Values calculated by the modeling software for thecombination of existing single pane window and the various insert windowconfigurations modelled. The U-Value is a measure of the insulativevalue of the window configuration and how much energy is lost or gainedthrough the window by heat conduction. A lower U-Value means that lessheat can be conducted into or out of a building through the windows overa given period of time. All of the insert window configurations modeleddemonstrated significantly lower U-Values than the original single panewindows by themselves. In the case of the single-pane insert windows,configurations A, C, D, and B-2 demonstrated similar U-Value reduction.Configuration B, while still significantly better insulating than thesingle pane base case, demonstrated a slightly higher U-Value than theother single-pane insert window configurations—this may be due to thelack of a low-E coating. The IGU insert window configurations E, F, andF-2 provided even lower U-Values than the single-pane insert windowconfigurations because of the extra layer of glass and the extra airspace in the IGU.

The insert windows demonstrated reduced U-values relative to a singlepane of glass; inclusion of a low-E coating provided a lower U-value(compare configurations A and B). However, the relative position of thelow-E coating and VTOF did not affect the U-value as much (compareconfigurations A and B-2; C and D), IGU insert windows configurationsdemonstrated improved U-values, again arrangement and configuration oflow-E and VTOF did not affect the U-value greatly configurations E, Fand F-2).

Example 17 Energy Consumption Model

FIG. 20 shows an example of the overall energy impact of several insertwindow configurations on the annual energy use of a medium-sized officebuilding in four different locations. The modeling was done using the USDepartment of Energy's EnergyPlus software version 6.0. Referencebuilding input files (also from the US Department of Energy) forpre-1980 construction were used with minor modifications. Briefly, thewindow-to-wall ratio was increased from 33% to 66%; the U-values andSHGC of the input files were replaced with the U-values and SHGC valuesobtained from the model described in Example 16; and the software wasset to switch the smart insert windows from the light state to the darkstate when the solar irradiance exceeded 100 W/m² and the exteriortemperature was higher than 10° C. Four different cases were considered:

1) original single pane windows with no insert window (striped bars);

2) single pane smart insert window with variable transmittance opticalfilter (equivalent to configuration B-2 above) (solid bars);

3) double pane IGU smart insert window with variable transmittanceoptical filter (configuration E above) (checked bars); and

4) single pane clear insert window with float glass and no low-Ecoatings or any variable transmittance film (open bars).

Simulations were run for each case in four different locations: LosAngeles, Chicago, Seattle, and Phoenix. As can be seen in FIG. 20,energy use could be significantly reduced in all four locations throughthe addition of an insert window to the existing single pane window. Inall locations, the variable transmittance single-pane window(configuration B-2) reduced the energy used by the building more thanthe plain clear insert window. The double-pane insert window(configuration E) reduced the energy used by the greatest margin in allfour locations. The energy savings result from both reduced SHGC andreduced U-Value. The greatest energy savings result in Phoenix andChicago, which are similar in latitude to Los Angeles and Seattlerespectively, but have more extreme climates due to their inlandlocation.

Other Embodiments

It is contemplated that any embodiment, aspect, example, method,composition, or element discussed in this specification may beimplemented or combined in any suitable manner with any otherembodiment, aspect, example, method, composition, or element.

The present invention has been described with regard to one or moreembodiments. However, it will be apparent to persons skilled in the artthat a number of variations and modifications can be made withoutdeparting from the scope of the invention as defined in the claims.Therefore, although various embodiments of the invention are disclosedherein, many adaptations and modifications may be made within the scopeof the invention in accordance with the common general knowledge ofthose skilled in this art. Such modifications include the substitutionof known equivalents for any aspect of the invention in order to achievethe same result in substantially the same way. Numeric ranges areinclusive of the numbers defining the range. In the specification, theword “comprising” is used as an open-ended term, substantiallyequivalent to the phrase “including, but not limited to,” and the word“comprises” has a corresponding meaning. As used herein, the singularforms “a”, “an” and “the” include plural referents unless the contextclearly dictates otherwise. Citation of references herein shall not beconstrued as an admission that such references are prior art to thepresent invention, nor as any admission as to the contents or date ofthe references. All publications are incorporated herein by reference asif each individual publication was specifically and individuallyindicated to be incorporated by reference herein and as though fully setforth herein. The invention includes all embodiments and variationssubstantially as hereinbefore described and with reference to theexamples and drawings.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as is commonly understood by one of ordinary skillin the art to which this invention belongs. If a definition set forth inthis section is contrary to or otherwise inconsistent with a definitionset forth in the documents that are herein incorporated by reference,the definition set forth herein prevails over the definition that isincorporated herein by reference.

What is claimed is:
 1. A device comprising: a) a variable transmittanceoptical filter comprising: i. a first substantially transparentsubstrate, comprising a first electrode; ii. a second substantiallytransparent substrate comprising a second electrode; iii. a switchingmaterial disposed between, and operatively coupled to, the first andsecond electrodes, the switching material transitionable from a firstlight transmittance state to a second light transmittance state withapplication of voltage to the switching material, and transitionablefrom the second light transmittance state to the first lighttransmittance state with application of a non-electrical stimulus; b) anenergy harvesting power source; and c) an electrical system configuredto receive power from the power source and to provide a voltage to thefirst electrode and the second electrode.
 2. The device according toclaim 1, wherein the variable transmittance optical filter is a film. 3.The device according to claim 1, wherein the first transmittance stateis a dark state and the second transmittance state is a faded state. 4.The device according to claim 1, wherein the non-electrical stimulus isexposure to light.
 5. The device according to claim 1, wherein thenon-electrical stimulus is UV light.
 6. The device according to claim 1,wherein the switching material comprises a photochromic andelectrochromic compound.
 7. The device according to claim 6, wherein thephotochromic and electrochromic compound of the switching material is adiarylethene.
 8. The device according to claim 1, wherein the switchingmaterial is transitionable from a faded state to a dark state with lightcomprising wavelengths of about 350 to about 420 nm, or of about 365 toabout 420 nm, or of about 375 to about 420 nm, or of about 375 to about420 nm, or of about 380 to about 420 nm, or of about 385 nm to about 420nm, or any amount or range therebetween.
 9. The device according toclaim 1, wherein the electrical system comprises an energy storagecomponent configured to receive and store power from theenergy-harvesting power source, and to provide power for application ofthe voltage to the switching material.
 10. The device according to claim1, wherein the energy-harvesting power source is disposed on a surfaceof the first substrate, a surface of the second substrate, or a surfaceof the first substrate and a surface of the second substrate.
 11. Thedevice according to claim 1, wherein the energy-harvesting power sourceis selected from the group consisting of a piezoelectric power source, aphotovoltaic power source, a vibrational energy-harvesting power sourceor a thermal energy-harvesting power source.
 12. The device according toclaim 11, wherein the photovoltaic power source has an area from about1% to about 25%, or from about 1% to about 10%, or from about 1% toabout 5% of the area of the variable transmittance optical filter, orany amount or range therebetween.
 13. The device according to claim 1,wherein the energy harvesting power source provides from about 0.0001 Wto about 25 W per meter square of optical filter area.
 14. The deviceaccording to claim 1, wherein the voltage applied to the first andsecond electrodes is from about 0.1V to about 5V or from about 0.5V toabout 3V or from about 1.2V to about 2.5 V, or from about 1.8V to about2.1 V.
 15. The device according to claim 1, wherein the firsttransmittance state has visible light transmission of less than 50%, orless than 40% or less than 30% or less than 20% or less than 10%; and/orwherein the second transmittance state has visible light transmission ofat least 50%, or at least 60% or at least 70% or at least 80% or atleast 90%.
 16. The device according to claim 1, wherein the firsttransmittance state has visible light transmission from about 5% toabout 50%, or from about 5% to about 40%, or from about 5% to about 30%,or from about 5% to about 20%, or from about 5% to about 10%, or anyamount or range therebetween.
 17. The device according to claim 1,wherein the second transmittance state has visible light transmissionfrom about 50% to about 99%, or from about 60% to about 95%, or fromabout 70% to about 95%, or from about 80% to about 95%, or any mount orrange therebetween.
 18. A window or opthalmic device comprising thedevice according to claim
 1. 19. A window comprising: a) a pane having avariable transmittance optical filter disposed on a first side,comprising: i a first substantially transparent substrate, comprising afirst electrode; ii a second substantially transparent substratecomprising a second electrode; and iii a switching material disposedbetween, and operatively coupled to, the first and second electrodes,the switching material transitionable from a first light transmittancestate to a second light transmittance state with application of voltageto the switching material, and transitionable from the second lighttransmittance state to the first light transmittance state withapplication of a non-electrical stimulus; b) an electrical systemconfigured to receive power from an energy harvesting power source andprovide a voltage to the first and second electrodes of the variabletransmittance optical filter; and c) a first frame surrounding the pane,the first frame configured for slidable mounting within a second frame,the second frame configured for mounting in an existing window openingof a building.
 20. A method for preparing a self-powered variabletransmittance optical device, the method comprising: a) disposing alayer of switching material on a substantially transparent substrate,the switching material capable of transitioning from a light state to adark state on exposure to UV radiation and from a dark state to a lightstate with application of an electric voltage, wherein a first andsecond electrode are disposed such that the switching material isproximate with the first and second electrodes; b) providing anenergy-harvesting power source; and c) providing an electrical systemconfigured to receive power from the energy harvesting power source andto provide power to the first electrode and the second electrode forapplication of the electric voltage through the first and secondelectrodes.